Directions
BEAT butter, brown sugar, granulated sugar, vanilla extract and salt in large mixer bowl until creamy. Beat in egg yolk. Gradually beat in flour. Stir in morsels. Shape dough into 2 round discs; wrap in plastic wrap. Refrigerate for about 1 hour or until firm.
PREHEAT oven to 350° F.
ROLL each disc to 1/4-inch thickness between two sheets of waxed paper. Cut into shamrock shapes; place on ungreased baking sheets.
BAKE for 9 to 11 minutes or until golden brown. Cool on baking sheets for 2 minutes; remove to wire racks to cool completely. Spread with frosting; sprinkle with coarse sugar.