PREHEAT oven to 325° F. Grease large baking sheet.
PLACE whole bar of dough in prepared pan. Allow to soften for 5 to 10 minutes. Using fingertips, pat dough gently to form an 8- or 9-inch shamrock shape.
BAKE for 20 to 23 minutes or until light golden brown. Cool on baking sheet for 2 minutes; carefully loosen cookie with a spatula. Cool completely on baking sheet on wire rack.
DECORATE as desired.