This was in the New York Times last week. Amanda Hesser shared a recipe from an early 20th century cookbook (1907) for Soupe à l’Oignon Gratinée. It doesn’t call for any broth and ends up being more of a casserole. A really delicious casserole.
Soupe à l’Oignon Gratinée
1 baguette, cute into 1/2″ slices, about 25 to 30
9 TBL softened butter
9 ounces of Emmental cheese, finely grated
8 medium yellow onions, thinly sliced (about 8 cups)
1 TBL kosher salt, more to taste
1 cup tomato puree
1. Toast the baguette slices and let them cool. Spread a generous layer of butter on each slice (about 5 TBL), then lay the slices close together on a baking sheet and top with all but 1/2 cup of cheese.
2. In a large saucepan, melt the remaining 4 TBL of butter over medium heat. Add the onions, season with salt and saute, stirring occasionally, until very soft and golden, about 15 minutes.
3. In a 5-quart casserole, arrange a layer of bread slices, (about 1/3 of them). Spread 1/3 of the onions on top, followed by 1/3 of the tomato puree. Repeat for 2 more layers. Sprinkle with the remaining 1/2 cup of cheese. To avoid boiling over, the casserole must not be more than 2/3 full.
4. In a saucepan, bring 1 1/2 quarts 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.
5. Preheat the oven to 350 degrees. Put the casserole on the stove and simmer uncovered for 30 minutes, then transfer to the oven and bake uncovered for 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.
I didn’t find this at all difficult to make. I got the baguette sliced at the bakery. The most onerous tasks were slicing the onions and grating the cheese. One thing I might try differently is to use a technique from this recipe and fry the baguette slices. At the very least, I would have spread the bread with the butter and the cheese sooner rather than later. I also cooked the onions for about a half hour. I think you get more depth if you cook them longer. It’s not as good the second day and this recipe does make a lot.
What you end up with (I don’t have a digital camera so you’ll just have to Google for images yourself) is more casserole like than soup like. The layers of bread soak up the salted water and blend with the butter, cheese, and tomato puree and puff up. The flavors are amazing and comforting. Everyone waxes eloquently about the crust–and justifiably so–this is the food of the gods.