Last night, we ventured out to a neighborhood holiday pot-luck. It was the first time we'd done anything like it since our move, and I'm a little out of practice with cooking for crowds, so my contribution was a standard that I could do without thinking about it, an extravagant but very easy potato gratin.
And as it always does, my gratin dish came home scraped clean.
It's a simple concoction of thinly-sliced potatoes, cream, and good cheese for which I can't take any credit, since the recipe is a timeless classic French one, and my version was inspired by the one Ina Garten shared in her first Barefoot Contessa cookbook.
Perfect not only for pot-lucks but for any holiday gathering, it'll go with anything and is at home anywhere, from the most casual family buffet to the most formal white-cloth-and-silver laid tables. Best of all, it can be made ahead and gently reheated.
Classic Potato Gratin
The large russet potatoes that are sold loose are very large indeed, one of them weighing as much as a pound. Three of those are usually just right, but if the potatoes you're using are smaller, you might need 4 or even 5, so measure by weight rather than count. And the potatoes needn't be russets: just make sure the ones you choose are mature and starchy.
If a really good genuine Gruyère isn't available where you live, use the best hard-grating cheese you can find. An aged, extra-sharp cheddar won't be quite the same but is still very good, and would be preferable to a domestic so-called "Swiss" cheese.
And within reason, feel free to make it your own simply by adding herbs, or a bit of chopped ham, or, as Ms. Garten presented it, thinly-sliced sautéed fennel. Just keep in mind that good potatoes and cheese don't need a lot of help, so keep it simple.
2 large yellow onions (not sweet onions), thinly sliced
2 tablespoons unsalted butter
3 pounds russet (baking) potatoes, about 3-4 large
8 ounces Gruyère cheese, coarsely grated (about 2½ cups)
2 cups (1 pint carton) heavy cream
Salt and whole black or white pepper in a mill
Whole nutmeg in a grater
1 ounce Parmigiano-Reggiano cheese, finely grated (about ¼ cup)
1. Position a rack in the center of the oven and preheat to 350° F. Butter a 3-quart (about 10x15x2-inches) gratin or baking dish. Put the onions and butter in a large pan over medium heat and sauté, stirring often, until golden brown, about 10 minutes. Scrub the potatoes under cold running water, peel, and thinly slice them with a really sharp knife (a ceramic one will keep them from discoloring) or a mandoline.
2. Put the potatoes in a large bowl and add the cream. Set aside half a cup of the Gruyère and add the rest to the potatoes along with the onions. Season liberally with salt, pepper, and nutmeg and gently toss until well-mixed. Pour this into the casserole, spread evenly, then press down and level the top. Sprinkle with the remaining Gruyère and Parmigiano.
3. Bake in the center of the oven until it's golden brown, bubbly to the center, and the potatoes are tender, between 1¼-1½ hours, depending on your oven and the dish you've used. Check after about forty-five minutes and turn the dish if it appears to be browning unevenly. To test for doneness, insert a sharp paring knife or toothpick into the center. It should slip in easily with no resistance. Serve hot.
Make ahead notes: If you're making it ahead, let it cool completely, then cover tightly with foil, making sure that it doesn't touch the top of the gratin, and if you're making it more than four hours ahead, refrigerate it until about an hour and a half before you plan to serve it. Reheat it, still covered, in an oven preheated to 350 degrees, for about half an hour, or until it's hot at the center, removing the foil during the last five minutes.