French Onion Soup - cooking recipe

Ingredients

4 large white onions
2 large yellow onions
1 tsp. dry mustard
1 tsp. salt
1 tsp. pepper
1/4 c. butter
4 c. beef stock
4 c. chicken or poultry broth
1 loaf French bread
Parmesan cheese
Gruyere cheese
1 bottle dry sherry

Preparation

Slice onions paper thin.
Fill large pot to the top with onions.
Add 1/4 cup of butter and simmer on low until onions are translucent.
Mix in 1 teaspoon of dry mustard, salt and pepper. Add equal amounts of beef and chicken stock and 1/4 cup of sherry. Cook on low (without boiling) for 6 to 8 hours a day, for two days. Add sherry to replace fluid as it evaporates.
Cut French bread into thin slices and place on a baking sheet.
Bake in oven on low temperature for 3 to 4 hours, until hard.
Grate Gruyere cheese on bread and continue baking for 1 hour.