4 to 5 lg. onions, thinly sliced
6 tbsp. butter
3 tbsp. all-purpose flour
2 tsp. salt
1 to 1 1/2 tsp. pepper
3 qts. water
1/4 c. dry sherry, or to taste
3 tbsp. chicken stock base
3 tsp. beef stock base
French bread
Melted butter
Parmesan cheese
Grated Swiss cheese

In a large Dutch oven, cook onion slices in butter until tender. Blend in flour, salt and pepper. Add water, sherry, chicken base and beef base. Simmer 2 to 4 hours.

One-half hour before serving, slice French bread 1 inch thick and brush both sides with melted butter. Place slices on baking sheet and toast at 350 for 15 to 20 minutes. Ladle soup into bowls, add toast slices and sprinkle on combined cheeses.