What makes this chicken liver mousse so special is its coarse texture and use of very little fat. Most recipes for liver mousse made from cooked chicken livers contain copious amounts of butter or other fats for a moist and creamy texture. This version gets moisture, flavor and texture from onions, shallots and apple. For best results, do not overcook the chicken livers, which should be pink on the interior. Serve with mustard and crackers or toasted bread.