Preheat oven to 350 degrees F
Cream butter and sugar. Beat in egg yolks.
Beat in powdered sugar. Then add flour and beat until well incorporated.
Roll into balls about 1/2 inch diameter. Place on ungreased cookie sheet about 1 inch apart. With your fingertip make a well in the top. Fill 3/4 with apple butter. Bake 17 minutes. Cool on wire rack. Store in a covered container.