Summary: This recipe, from Ali-Bab's “Gastronomie Pratique,” first appeared in The Times in a 1974 article by Craig Claiborne. I discovered it in a 2007 NY Times Magazine Recipe Redux by Amanda Hesser. It's been a favorite ever since- decadent, simple, hearty, fabulous. Most of the instructions are from the 2007 piece but I've changed or edited several things, some of which I've noted.
Yield: 6-8 servings
- 1 baguette, cut into 1/2-inch slices (about 25 to 30)
- 7-9 tablespoons butter, softened
- 9 ounces Emmental cheese (I use Gruyère!), finely grated
- 12 cups yellow onions, thinly sliced (7-8 medium onions)
- 1 tablespoon kosher salt, more to taste
- 1 cup tomato purée (use crushed canned tomatoes, or make your own)
Toast the baguette slices and let them cool. Spread some butter on each slice (the original recipe calls for using five tablespoons of butter here; I probably use three), then lay the slices close together on a baking sheet and set aside.
In a large saucepan, melt the remaining four tablespoons butter over medium heat. Add the onions, season with salt and sauté, stirring occasionally, until very soft and golden, about 15 minutes.
In a 5-quart casserole (I use a stock pot because you need to first cook this on the stove and then transfer the the oven), arrange a layer of bread slices (about a third of them). Spread a third of the onions on top, then some of the cheese, and then about a third of the tomato purée. Repeat twice, reserving about a half-cup cheese for sprinkling over the top. Finish things off with your remaining cheese. To avoid boiling over, the casserole must not be more than two-thirds full.
In a saucepan, bring 1½ quarts of water to a boil. Add the salt. Very slowly pour the salted water into the casserole, near the edge, so that the liquid rises just to the top layer of cheese without covering it. (Depending on the size of your casserole, you may need more or less water.)
Preheat the oven to 350 degrees. Put the casserole on the stove and simmer uncovered for 25-30 minutes, then transfer to the oven and bake uncovered for about 1 hour. The soup is ready when the surface looks like a crusty, golden cake and the inside is unctuous and so well blended that it is impossible to discern either cheese or onion. Each person is served some of the baked crust and some of the inside, which should be thick but not completely without liquid.