Wash, dry, and chop livers. Sauté mushrooms in butter for 5 minutes. Remove mushrooms with a slotted spoon and set aside. Sauté onions in same pan and cook 5 minutes. Add livers to pan, stir and cook until still barely pink inside, about 5 minutes. Put into blender; add mushrooms, cognac, and seasonings. If mixture is too thick, add more melted butter (1 or 2 tablespoons). Pack in crocks or a mold and chill. Serve in crock or unmold and decorate with parsley and mushrooms. Serve at room temperature. Freezes well.