Sauté chicken livers in ¼ cup butter about 5 minutes or until thoroughly cooked.  Remove from skillet and set aside.  Sauté onion in same pan about 3 minutes or until softened.  Puree liver and onion in food processor or blender or finely grind in food grinder.  Add brandy, mustard, allspice and pepper.  Puree or grind again until mixture is blended and smooth.  Spread in shallow pan; refrigerate, covered, until thoroughly chilled.  Soften remaining butter and beat until light and creamy; add chilled liver mixture and mix well.  Fold in pistachios; salt to taste.  Spoon into crock or mold.  Cover; refrigerate until firm.