A golden cheese crust is only half the pleasure of a potato gratin: underneath are thin slices that have slowly softened in seasoned cream. To make these creamy, cheese-topped potatoes, slice them evenly, layer them with the sauce, and bake until a knife slips through the center.
A short rest after baking gives the sauce time to settle around the layers. The result is a comforting side dish that can be spooned beside roast chicken or served with a crisp green salad.
Potatoes au Gratin: Ingredients and Equipment
For a 2-quart baking dish and about six servings, gather:
- 2 pounds Yukon Gold potatoes
- 1 tablespoon butter, for the dish
- 1 1/2 cups heavy cream
- 1/2 cup whole milk
- 2 garlic cloves, finely minced
- 3/4 teaspoon salt
- 1/4 teaspoon black pepper
- A small pinch of ground nutmeg, optional
- 1 1/2 cups shredded Gruyère, about 6 ounces
Yukon Gold potatoes hold their shape while becoming tender and creamy. Russets also work, though their higher starch content gives the layers a softer texture. Gruyère melts well and has a nutty flavor; a mild Swiss cheese or sharp cheddar makes a good substitute. Grate the cheese from a block for even melting.
You will need a sharp knife or mandoline, a small saucepan, foil, and a baking sheet to catch any bubbling cream. If you use a mandoline, use its hand guard and work carefully as the potato gets smaller.
Slice for Even Cooking
Heat the oven to 375°F and butter the baking dish. Scrub and peel the potatoes, then cut them into slices about 1/8 inch thick. Keep the slices as uniform as you can: thick pieces take longer to soften, while very thin ones can break down before the center is done.
A mandoline makes consistent rounds quickly, but a knife works well. Cut a thin slice off one side of a potato to give it a flat surface, set it cut-side down, and slice across. As you work, keep the rounds together so they are easy to arrange in layers.
Avoid rinsing the slices after cutting. Their surface starch helps the cream thicken around them as they cook. Prepare the cream mixture and pan first so you can assemble the potatoes promptly after slicing.
Layer the Potatoes, Cream, and Cheese
Warm the cream, milk, garlic, salt, pepper, and nutmeg in a small saucepan over medium-low heat until steaming, stirring occasionally. There is no need to boil it. Warming distributes the seasoning and gives the garlic time to flavor the liquid.
Arrange half the potato slices in overlapping rows in the buttered dish. Pour over half the warm cream mixture and scatter on half the cheese. Add the remaining potatoes, pour over the rest of the mixture, and finish with the remaining cheese. Press the slices gently into the liquid; the top may sit just above it. The layers do not have to look perfect to cook beautifully.
For potatoes au gratin with a more pronounced savory note, replace a portion of the Gruyère with sharp cheddar. Keep the total quantity of cheese the same on your first attempt so the sauce and topping stay in balance.
Bake, Test, and Rest
Set the dish on the baking sheet. Cover loosely with foil and bake for 45 minutes. Remove the foil and bake for another 25 to 35 minutes, until the top is golden and the cream bubbles at the edges. If the surface browns too quickly, lay the foil back over it loosely while the middle finishes cooking.
Color is a tempting clue, but tenderness tells you when au gratin potatoes are ready. Insert a thin knife through the center to the bottom of the dish; it should slide through with little resistance. Test a second spot if the slices overlap heavily. Thicker layers or a deeper dish may need extra time.
Let the potato gratin stand for 15 to 20 minutes before serving. The hot cream thickens as it cools slightly, so the layers hold together better on the plate and the sauce is less likely to run. The resting time also makes the first bite more comfortable to eat.
Serve and Store
Serve au graten potatoes with roast chicken, baked ham, or sautéed greens. The rich cheese and cream are especially pleasant next to a sharp vinaigrette or something green and crisp. Use a broad spoon to lift portions, reaching beneath the bottom layer so each serving gets some sauce.
Refrigerate leftovers in a covered container within two hours. Reheat portions until hot throughout, adding a small splash of milk if the sauce looks dry. Covering the dish during reheating helps the potatoes warm before the top darkens further.
If the Center Is Still Firm
The most common setback is a browned top over potatoes that are still firm in the middle. If the knife catches, cover the dish loosely with foil and return it to the oven for 10 minutes, then test again. Repeat until the center is tender. Next time, cut the slices more evenly and use a dish wide enough to keep the layers from becoming too deep.