Heat oven to 350°F. On ungreased large cookie sheet, press cookie dough pieces together into shape of large egg, about 1/2 inch thick.
Bake 18 to 21 minutes or until golden brown and set. Cool completely on cookie sheet on cooling rack, about 30 minutes.
Attach star tip to tube of white icing; outline cookie cake with white icing. Sprinkle with pastel candy sprinkles. Decorate as desired with remaining white icing, the pink and purple icing, and sparkling sugar.