Melt butter in large heavy skillet. Add onions and chicken livers and saute, stirring until livers are lightly browned. Cool slightly, and drain off any juices. Combine liver and onions with eggs and parsley in a food processor. Blend until smooth. Mix in mayonnaise, salt, pepper, and Worcestershire sauce. Pour pate mixture into bowl. Chill overnight. Garnish with additional parsley.
