4 large onions, sliced
1/4 cup butter1 tbsp flour
1/2 cup shredded Mozzarella cheese
6 cups (48 oz) beef broth
a few drops hot pepper sauce
6 slices French bread, toasted, or croutons

Cook onions in butter until transparent. Add flour; cook, stirring, until flour is well blended into the butter. Transfer onion mixture to slow cooker. Add beef broth and hot sauce. Cook on low for 6 to 8  hours or high 3 to 4 hours. Ladle soup into oven-proof bowls. Top with bread and some of the shredded cheese. Broil until cheese melts.

Serves 6.