Chop finely the onions, garlic and 7 ounces of the mushrooms. Brown onions in oil, then add garlic and saute briefly. Add mushrooms. Saute briefly. Add tomatoes, fennel, bay leaf, salt and pepper. Simmer gently for 10 minutes. Remove from heat and pass through a sieve or food mill (not a food processor). Add a dash of Tabasco. (Sauce can be made ahead and refrigerated.) Slice remaining mushrooms and saute for 3-5 minutes in approximately 2 tablespoons butter. In a large saute pan, brown fish in butter. Pour warm cognac over fish and flambe. Place fish in baking dish, pour sauce over and garnish with sauteed mushrooms. Bake 15 minutes in a 400'F. oven. Serve with rice. Nutrition Analysis per Serving: 337 calories; 18 grams fat; 67.4 milligrams cholesterol; 170 milligrams sodium; 50% of calories from fat.