A heavy 4-quart saucepan or casserole
3 Tbsp butter
1 Tbsp olive oil or cooking oil
About 1-1/2 lbs or 5-6 cups thinly sliced yellow onions
1 tsp salt
1/2 tsp sugar
3 Tbsp flour
2 quarts hot beef bouillon (you may dilute canned bouillon with 2 cups of water)
1 cup red or white wine
1 bay leaf
1/2 tsp sage
Salt and pepper to taste
Melt the butter with the oil in the saucepan or casserole, add the sliced onions and stir up to coat with the butter. Cover the pan and cook over moderately low heat for 15 to 20 minutes, stirring occasionally, until onions are tender and translucent. Then unover the pan, raise heat to moderately high, and stir in the salt and sugar. (Sugar, by caramelizing, helps onions to brown.) Cook for about 30 minutes, stirring frequently, until onions have turned an even deep golden brown.
Then lower heat to moderate, stir in the flour, and add a bit more butter if flour does not absorb into a paste with the onions. Cook slowly, stirring continually, for about 2 minutes to brown the flour lightly. Remove from heat.
Pour in about a cup of the hot bouillon, stirring with a wire whip to blend flour and bouillon. Add the rest of the bouillon and the wine, bay, and sage, and bring to the simmer. Simmer slowly for 30 to 40 minutes, season to taste with salt and pepper, and the soup is done. If you are not serving immediately, let cool uncovered, then cover and refrigerate.
Serve with French bread and grated Parmesan cheese.