In a small bowl, beat the butter, flour and cream. Cover and refrigerate overnight. Divide into 3 balls. On a lightly floured surface, roll out dough to 1/8-in. thickness. Cut with a floured 1-1/4-in. round cookie cutter. Place 1 in. apart on ungreased baking sheets. Sprinkle with sugar. Prick each cookie 3-4 times with a fork. Bake at 375° for 7-9 minutes or until set. Remove to wire racks to cool. In a small bowl, combine the butter, confectioners’ sugar, vanilla and egg yolk. Remove half to another bowl; tint one portion of filling with red food coloring and the other half with green. Carefully spread filling on bottom of half of the cookies; top with remaining cookies.