Slice onions into 1/8" thickness. In large soup pot, melt butter over low heat. Add onions and saute slowly for 1 1/2 hours. Add seasoning and flour and continue to cook over low heat for additional 10 minutes. Add beef broth and simmer slowly for 2 hours. Add wine and continue cooking 20 minutes. Remove bay leaf and season to taste. Can be refrigerated overnight.
To serve, heat soup and fill fireproof bowls (or individual casseroles) with 8 oz. soup, top with slices of French bread to cover and top with 1 1/2 oz grated cheese. Place bowls under broiler until cheese bubbles and turns golden brown (approximately 3-5 minutes). Freeze any unused soup. 16 servings.