French Onion Soup From Joy of Cooking - About 8 cups

The secret to this beloved classic is long, slow cooking of the onions to allow their natural sugars to caramelize; this gives the soup its characteristic depth of flavor and rich mahogany color.

Heat in a soup pot over medium-low heat until the butter is melted:
2 tablespoons unsalted butter
2 tablespoons olive oil

Add and stir to coat:
5 medium onions, thinly sliced
Pinch of dried thyme

Cook, stirring occasionally, and keeping a vigilant eye on the onions so they do not scorch, over medium heat. As soon as they start to brown, after about 15 minutes, reduce the heat to medium-low and continue to cook, covered, stirring more often, until the onions are a rich brown color, about 40 minutes. Stir in:
2 tablespoons dry sherry or cognac

Increase the heat to high and cook, stirring constantly, until all the sherry has cooked off. Stir in:
3 ½ cups Brown Beef Stock, Vegetable Stock, or Brown Chicken Stock

Bring to a boil; reduce the heat, and simmer, partially covered, for 20 minutes. Season with:
1 to 1 ½ teaspoons salt
¼ to ½ teaspoon ground black pepper

Place 8 ovenproof soup bowls or crocks on a baking sheet. Ladle the hot soup into the bowls and top each serving with:
1 to 3 slices French bread, toasted if fresh

Sprinkle each bowl with:
3 tablespoon grated Gruyere cheese

Broil or bake in a 450 F oven until the cheese is melted and starting to brown. Serve immediately.