Italian Potato Gratin | Gratin di Patate alla Fontina
A gratin is judged on a cut face. Lift out the first portion and you should see distinct layers of potato held by a set custard of milk, cream and melted Fontina, with a dark blistered crust on top and no loose liquid running into the gap. Nothing about that is accidental. It comes from the thickness of the slice, from cooking the potatoes in the dairy first, and from the rest that almost everyone skips.
Fontina DOP is what separates this from a French gratin. It is a washed rind mountain cheese from Valle d'Aosta with a high moisture content and a soft elastic paste, and it melts into a smooth savoury body rather than breaking into strings or oil. Parmigiano Reggiano goes in alongside it, not for melting but for salt, glutamate and the dry surface that browns properly under heat.
The dish wants to be rich and defined at the same time, which are competing aims. The version below keeps the dairy short of a flood, uses the potato itself to thicken what is there, and finishes hot so the top sets into a crust while the layers underneath stay tender.
Yield: 6 servings as a side dish. Prep: 30 minutes. Cook: 1 hour 10 minutes. Rest: 25 minutes. Total: about 2 hours 5 minutes. Difficulty: intermediate. Course: contorno. Region: Valle d'Aosta and the western Alpine valleys.
The Story
Fontina is one of the oldest documented cheeses in the Alps. It is made only from the raw whole milk of Valdostana cows, one milking at a time, in a valley that runs from Pont Saint Martin up to the Mont Blanc massif, and the name appears in written records by the eighteenth century although the cheese itself is far older. The wheels are ripened for at least three months in cold damp rock cellars, many of them disused mine galleries at Valpelline, where the humidity sits near saturation and the rind is washed and turned by hand. That environment is why the paste stays soft and why it melts the way it does.
Valle d'Aosta cooks it more often than it eats it raw. Fonduta valdostana, the cheese melted with milk and egg yolk, is the regional dish everyone knows, and the same instinct produces the gratins, the tortini and the polenta concia of the high valleys. Cheese was the protein of a place with very little arable land, and heat was the way to stretch it across a table of people who had worked outside all day.
The potato arrived in these valleys in the late eighteenth century and took hold quickly, because it grew where rye barely managed. Valle d'Aosta also spent centuries inside the Duchy of Savoy, with the Savoyard and Dauphinois valleys on the other side of the passes, so the layered potato gratin crossed the mountains in both directions and picked up the local cheese on the Italian side. The result is a dish that looks French on the surface and tastes entirely of its own valley underneath.
Ingredients
For the potatoes
Yellow fleshed waxy potatoes, 2 1/4 lb (1 kg)
Whole milk, 1 1/2 cups (360 ml)
Heavy cream, 1 cup (240 ml)
Garlic clove, halved, 1
Fresh bay leaf, 1
Freshly grated nutmeg, 1/4 tsp (0.5 g)
Fine sea salt, 1 1/2 tsp (9 g)
Freshly ground white pepper, 1/2 tsp (1 g)
For the cheese
Fontina DOP, rind removed, coarsely grated, 9 oz (250 g)
Parmigiano Reggiano, finely grated, 2 oz (55 g)
For the dish and the crust
Unsalted butter for the dish, 1 tbsp (15 g)
Parmigiano Reggiano, finely grated, 1/2 oz (15 g)
Unsalted butter, in small pieces, 1 tbsp (15 g)
Preparation
Step 1
Prepare the dish and the cheese. Heat the oven to 350°F (175°C). Rub a 9 by 13 inch (23 by 33 cm) baking dish with the cut face of the garlic clove, then butter it generously and keep the garlic for the dairy. Remove the rind from the Fontina and grate it coarsely. Grate the Parmigiano finely and keep the two in separate bowls, since they do different jobs and go in at different points.
Step 2
Slice the potatoes evenly and do not rinse them. Peel them and slice on a mandoline to an even 1/8 inch (3 mm). Thickness matters more than anything else: thicker slices stay firm in the middle while the outside overcooks, thinner ones collapse into a puree. Do not put the slices in water. The starch on each face is what thickens the dairy and glues the layers together, and washing it off is the commonest way this dish is ruined.
Step 3
Infuse the milk and cream. Put the milk, cream, garlic halves, bay leaf, nutmeg, salt and white pepper into a wide saucepan and bring it slowly to a bare simmer. Hold it just below simmering for 5 minutes so the aromatics open, then remove the bay leaf and the garlic. Taste and season firmly: it has to carry a kilo of potato, so it should taste slightly too salty on a spoon.
Step 4
Precook the slices in the dairy. Slide them into the hot liquid, separating them with your fingers, and cook at a gentle simmer for 8 to 10 minutes, moving them once or twice with a spatula. They should bend without breaking and still meet a little resistance at the centre. The liquid will thicken and turn opaque as starch leaves the slices. Do not let it boil hard or the cream will split.
Step 5
Layer the gratin. Lift about a third of the slices into the dish with a slotted spoon and spread them in overlapping rows like roof tiles, then scatter over a third of the Fontina. Repeat twice, pressing each layer flat. Pour the thickened dairy over and work the 2 oz of Parmigiano into the surface. The liquid should reach about three quarters of the way up the layers and no higher.
Step 6
Bake covered, then uncover for the crust. Cover the dish tightly with foil, set it on a tray and bake at 350°F (175°C) for 40 minutes. Remove the foil, scatter the last 1/2 oz of Parmigiano and the butter across the surface, raise the oven to 400°F (200°C) and bake 25 to 30 minutes more. It is ready when the top is deep golden and a thin knife slides through the centre with no resistance.
Step 7
Rest it before you cut it. Leave the dish on a rack for at least 25 minutes and up to 40. This is not a courtesy, it is part of the cooking. Straight from the oven the starch and the melted cheese are still fluid and a spoon pulls the layers into a pool. As it cools toward 150°F (65°C) the starch sets and the cheese firms, and a portion lifts out with a clean face.
Plating
Serve it hot but not straight from the oven, at around 150°F (65°C), which is where the cheese is still soft and the layers already hold. Cut generous squares with a thin knife, wiping the blade between cuts, and lift each one out with an offset spatula rather than a serving spoon so the cut face survives the journey to the plate.
Set the portion with the crust facing up and the cut face toward the diner, on a warm plate rather than a hot one. This is a side dish for roast meat, game or a braise, so it should sit beside the main item without sauce poured over it. No garnish is needed and parsley on top is a mistake. A grind of black pepper across the crust at the pass is the only finish that improves it.
Professional Technique
The whole structure of this gratin is built by precooking the slices in the dairy instead of pouring cold cream over raw potato. Potato starch granules begin to swell and burst at around 150°F (65°C), and once they do, they release amylose into whatever liquid surrounds them. Simmering the slices in the milk and cream for ten minutes puts that release exactly where it is useful: the liquid thickens into a light sauce that clings to every face, and the slices go into the dish already carrying it. Raw slices under cold dairy do the same thing much later and much less evenly, which is how you end up with a scorched top, a wet base and layers that slide apart.
The two cheeses are chosen for two different properties. Fontina DOP has roughly 45 percent fat in dry matter and a high moisture paste, so its casein network loosens smoothly between 130 and 160°F (55 and 70°C) and it flows rather than separating into strings and oil. Parmigiano is the opposite, dry, aged and low in moisture, and it will never melt cleanly. That is why it is used as seasoning and as crust: its free glutamates deepen the savour of the whole dish, and on the surface it dries and browns into the dark blistered top that a soft cheese alone cannot produce.
Texture and Moisture Control
The difference between a gratin and a casserole is how much free liquid is left at the end, and that is controlled at the moment of assembly. The dairy should reach about three quarters of the way up the layers, never covering them. What sits above that line is meant to be exposed to dry oven heat so it can dehydrate and brown, and a dish filled to the rim simply steams instead. The forty minutes under foil then cook the interior gently in trapped moisture, and the uncovered half hour drives off what is left on top.
Choice of potato decides how the layers behave. A waxy yellow fleshed variety holds its shape through two cookings and gives defined tiles on the cut face, while a very floury potato disintegrates in the simmering dairy and turns the gratin into a dense mash. The rest is temperature. Cream held at a hard boil will break and leave oil on the surface, so the precook stays at a bare simmer throughout. And the rest at the end is what actually sets the dish, because a gratin cut at 200°F (95°C) collapses and the same gratin cut at 150°F (65°C) does not.
Professional Mise en Place
The gratin can be assembled and baked ahead and finished at service, which is how it is handled in any kitchen that sends it out with a roast. Work in this order.
Equipment and tools
Mandoline with a guard, set to 1/8 inch (3 mm)
Wide saucepan or deep sauté pan for the precook
9 by 13 inch (23 by 33 cm) baking dish, ceramic or enamelled cast iron
Box grater, slotted spoon, offset spatula, foil and a baking tray
Probe thermometer for the rest
Prepared ahead
Fontina and Parmigiano grated and held separately, refrigerated, on the day
Dairy infused with the aromatics, up to 1 day ahead, strained and refrigerated
Gratin fully assembled and baked covered, cooled and refrigerated 1 day ahead
Dish rubbed with garlic and buttered, ready on the bench
Service setup
Oven at 400°F (200°C) for the uncovered crust stage
Gratin out of the refrigerator 1 hour before it goes back in
Thin knife, offset spatula and a cloth to wipe the blade between cuts
Warm plates and a pepper mill at the pass
Chef Tips
Buy Fontina DOP with the stamped rind and avoid anything sold simply as fontal or Swedish fontina. Those are industrial cheeses made from pasteurised milk with a far milder flavour and a waxier melt, and in a dish with only two cheeses in it the substitution is immediately obvious.
Grate the Fontina on the coarse holes rather than the fine ones. It is soft enough to smear and clog a fine grater, and larger shreds distribute better through the layers. If the cheese is too yielding to handle, put it in the freezer for fifteen minutes first and it will grate cleanly.
Use the mandoline and use the guard. Knife cut slices vary by a millimetre or two and that variation shows up as some layers still firm while others have gone to pulp. If you have no mandoline, the slicing disc of a food processor is a better answer than a knife.
Bake it the day before if you can. Stop after the covered stage, cool it, refrigerate it overnight and finish the uncovered crust stage before service. A night in the refrigerator lets the starch set completely, and the portions cut better than they ever will on the day.
Common Mistakes
Rinsing the sliced potatoes. Rinsing washes away the surface starch that thickens the dairy and binds the layers, and it leaves you with a gratin sitting in thin milk. Slice the potatoes and take them straight to the pan.
Drowning the layers in cream. Liquid above the top layer prevents the surface from drying and browning, and the dish comes out pale and soupy. Keep the dairy at about three quarters of the depth of the potatoes and no more.
Cutting it straight out of the oven. The starch and the cheese are still fluid at that temperature and the portion will collapse into a pool on the plate. Twenty five minutes of rest is the difference between a gratin and a bowl of hot cheese and potato.
Boiling the cream during the precook. A hard boil breaks the emulsion and leaves visible oil on the surface of the finished dish. Hold the pan at a bare simmer and move the slices gently.
Using floury baking potatoes. They fall apart during the ten minutes in the dairy and the gratin sets as a dense uniform mash with no visible layers. A waxy yellow fleshed potato is the only sensible choice here.
Wine Pairing
Valle d'Aosta Petite Arvine: The pairing from the same valley as the cheese, and the best on the list. Petite Arvine has unusually high acidity for an alpine white and a distinctly saline finish, and both work against the cream: the acid cuts the fat while the salinity meets the Fontina instead of being swallowed by it. Its grapefruit and rhubarb notes stay audible under a rich dish.
Valle d'Aosta Donnas DOC: The local nebbiolo, grown on terraces at the mouth of the valley in a lighter register than its Piedmontese relatives. Its firm acidity and fine dusty tannin scrub the palate between forkfuls, which a soft red cannot do against melted cheese. The dried rose and tar notes sit beside the nutmeg, and it is light enough not to bury a side dish.
Alto Adige DOC Pinot Nero: A red for anyone who finds nebbiolo austere. Alpine pinot nero keeps its acidity and stays low in tannin, so it lifts the fat without adding grip of its own, and its red cherry and undergrowth character suits the browned crust. Serve it at around 57°F (14°C).
Valtellina Superiore DOCG: The other mountain nebbiolo, from the terraces above the Adda in Lombardy, and the choice when the gratin goes out beside game or a braise. It has more structure than Donnas and a savoury mineral edge that echoes the washed rind of the Fontina. Give it thirty minutes in the glass and the tannin softens.
Storage & Reheating
This is one of the few dishes that improves on the second day. Cool the gratin to room temperature within two hours, cover it tightly and refrigerate for up to 4 days. The starch sets further overnight and the layers cut far more cleanly cold than warm, which is why portioning it the day after and reheating squares is the professional approach.
Reheat portions in an oven at 350°F (175°C) for 20 to 25 minutes, uncovered, on a tray lined with baking paper. The crust crisps again and the interior comes back to temperature without drying. If the surface browns before the centre is hot, lay a loose sheet of foil over it for the last few minutes. A microwave softens the crust completely and pushes moisture out of the layers, so use it only when speed matters more than the dish.
The gratin freezes acceptably but not well. Cut it into portions, wrap each one and freeze for up to 2 months, then thaw overnight in the refrigerator before reheating as above. Expect the texture to be slightly grainier, since the dairy emulsion and the potato cells both suffer on thawing. Never freeze it before baking: raw sliced potato turns dark and watery in the freezer and no amount of oven time recovers it.
Nutrition
Per serving, based on 6 side dish portions:
Calories: 480 kcal
Total Fat: 31 g
Saturated Fat: 19 g
Trans Fat: 0.9 g
Unsaturated Fat: 9 g
Cholesterol: 95 mg
Sodium: 780 mg
Total Carbohydrates: 32 g
Fiber: 3 g
Total Sugars: 6 g
Added Sugars: 0 g
Protein: 19 g
Lactose: 4 g
Principal micronutrients: calcium, phosphorus, potassium, vitamin A, vitamin B12, zinc
These figures are estimates. Sodium varies most, since both Fontina and Parmigiano carry their own salt and the seasoning of the dairy has to be judged against them.
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