4 slices dried French bread, toast under broiler
6 tbsp. butter
4 onions, thinly sliced (4 to 5 c.)
1 tbsp. sugar
2 tsp. flour
1 tsp. dry mustard
2 (10 3/4 oz.) cans condensed chicken broth
1/4 c. dry white wine
2 tsp. Worcestershire sauce
1/4 c. grated Parmesan cheese
1 c. Gruyere cheese

In heavy skillet, cook onions in butter until onions are light golden brown. Stir in sugar, flour, and dry mustard; cook 1 minute. Stir in chicken broth, white wine, and Worcestershire sauce. Bring to a boil, then simmer 10 to 15 minutes.

Ladle soup into oven-proof serving bowls. Top each serving with a toasted French bread slice, grated Parmesan, and Gruyere cheese. Place bowls on a baking sheet. Place 4 inches from broiler heating element and broil 2 to 3 minutes to melt cheese.