Ingredients
1/2 cup unsalted butter
3 tablespoons all-purpose flour
2 large white onions, chopped into small pieces
4 cups homemade or low-sodium canned chicken stock
4 cups homemade or low-sodium canned beef stock
1 teaspoon salt
1/4 teaspoon freshly ground pepper
18 thin slices French baguette
2 cups shredded Swiss cheese (1/2 pound)
Preparation
In a large, heavy-bottom saucepan, melt the butter over medium heat. Add flour and chopped onions; saute, stirring occasionally, until onions are soft and translucent, about 15 minutes.
Pour chicken and beef stocks into the saucepan, and stir to combine. Bring mixture to a boil. Reduce heat to low, and simmer 15 minutes. Add salt and pepper.
Heat broiler. Ladle soup into six 16-ounce ovenproof bowls, and float 3 slices of bread on top of each. Sprinkle the cheese over bread slices in each bowl, dividing evenly. Place bowls on a rimmed baking sheet, and broil until cheese is melted and bubbling, about 2 minutes. Let soup cool slightly before serving.