Wash the livers, remove any discolored areas and cover with " water.
Add the whole onion; bring to a boil and cook over low heat 5 minutes.
Melt the margarine in a skillet; saute the chopped onions until lightly browned.
Add the broth; cook 1 minute.
Use a blender for the livers and onions and run machine until smooth or chop the livers and onions very fine; blend in the salt, pepper and cognac.
Pack into a mold or bowl and chill.