1/2 stick butter
1 tablespoon olive oil
8 cups thinly sliced onion rounds (about 2-1/2 pounds)
1/2 teaspoon salt
1/2 teaspoon sugar
1 tablespoon flour
8 cups homemade beef stock or good quality store-bought stock (divided)
1 cup Chateau Grand Traverse Dry Riesling wine
8 thick slices of French bread, toasted
3/4 pound coarsely grated Gruyere (or mozzarella)
Melt both the butter and olive oil in a heavy saucepan over moderate heat. Stir in onions, cover, and cook slowly until tender, about 10 minutes. Blend in sugar and salt, increase heat to medium high and let onions brown, stirring frequently until dark walnut in color, 25-30 minutes.
Sprinkle in flour and cook slowly, stirring for 4 minutes. Remove from heat, let cool a moment, then whisk in 2 cups of hot stock. When well blended, bring to a simmer, adding rest of the stock and wine. Cover loosely and simmer very slowly for 1-1/2 hours, adding water if needed. Taste for seasoning.
Divide soup among 4 ovenproof bowls. Arrange toast on top of soup and sprinkle generously with grated cheese. Place bowls on cookie sheet and place under preheated broiler until cheese melts and forms a crust over the tops of the bowls. Serve immediately. (Note: Texas Toast can be substituted: Oven bake 3-4 minutes at 400 degrees and place on hot soup. Sprinkle grated cheese on top.)