Adapted from SeriousEats.com
- 1 pound sweet white or yellow onions, peeled and thinly sliced
- 2 cups dry white wine, such as Muscadet
- 2 tablespoons butter
- 6 cups chicken stock, preferably homemade
- 4 slices crusty bread or baguette
- 2 cups (5 ounces) freshly grated Gruyere cheese
Preheat the oven to 500°F. Combine the onions, wine, butter, and a large pinch of salt in a baking dish and cook, uncovered, until the wine is absorbed almost completely into the onions, and they are tender and golden, 45 minutes or perhaps a little longer.
In the meantime, bring the chicken stock to a simmer in a large saucepan. Season to taste with salt and pepper.
When the onions are finished, divide them among 4 deep broiler-safe bowls. Cover the onions with chicken stock to fill the bowls, and place a slice of bread on each. Distribute the grated cheese over the bread and broil until the cheese is golden and bubbling, 2 to 3 minutes.