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.