Preheat your oven to 350 degrees. In a medium bowl, cream butter until light and fluffy. Add cornstarch and powdered sugar and beat until combined. Beat in flour until thoroughly mixed. Drop by tablespoon onto ungreased baking sheets. Flatten dough with the bottom of a cup (dipped in powdered sugar to prevent sticking). Bake for 10 -12 minutes. Cool on wire rack and frost with Cream Cheese Frosting.

For the frosting, combine all ingredients together in a mixer fitted with a paddle attachment. Color with food coloring if desired.