Peel and slice onions thinly. Heat butter in a large sauce pan with a little sugar, add the onion rings and cook them very gently, over a low flame, stirring with a spoon until the rings are an even golden brown. Add beef stock gradually, stirring, until the soup begins to boil. Lower the heat, cover pan, and simmer gently for about 1 hour. Just before serving, add cognac, salt, and pepper. Serve in individual bowls containing buttered rounds of french bread covered with grated Gruyere cheese.{$7e}(Original recipe for 4)
