Recipe Notes Serves 4.
3 tablespoons olive oil
2 tablespoons unsalted butter
2 extra jumbo Spanish onions, quartered and sliced very, very thin
4 cups (32 ounces) beef stock
1 to 2 teaspoons Worcestershire sauce
Salt and pepper to taste
½ pound Gruyere (or similar dense and hearty Swiss cheese), grated
4 baguette slices, toasted on both sides
You’ll need four oven-proof bowls for this dish.
Warm a soup pot (preferably nonstick) over low heat.
Add the oil and butter, turn the heat up to medium, and add the onions.
Keeping the temperature as close to medium as you can, allow onions to caramelize to a deep, rich brown, stirring only enough to prevent the onions from burning (you may have to adjust the heat during this process).
When the onions are nearly done, turn the broiler on in the oven to let it come up to temperature. Meanwhile, add the beef broth and the Worcestershire sauce to the onions, simmer for 15 minutes, and season with salt and pepper to taste.
Place a baguette slice in each of the four oven-proof bowls, then evenly divide the soup. Sprinkle each bowl with a quarter of the grated cheese.
Place the bowls on a heavy-duty cookie sheet and place under the broiler.
Broil until the cheese is a bubbly light brown, only a couple of minutes. Be sure to use oven mitts to place the bubbling bowls of soup carefully onto plates.