The recipe yield is:
Blend butter and sugar; stir in egg yolk and vanilla. Sift flour and salt into bowl; mix well. Chill 1 hour. Roll into 1 inch balls. Dip into slightly beaten egg white. Roll in nuts. Place 1 inch apart on Cookie sheet. Bake 350-degrees F. 5 minutes. Press thumb gently in center of each; bake 5 minutes longer. Cool. Fill with frosting. Garnish with one peanut M&M on each cookie.
Desserts; Cookies; Candies; Frostings