Unmold 1 cake layer onto plate; spread with 1/2 cup Cool Whip
. Unmold second cake layer; carefully place on top of first layer. Frost top and side of cake with 2 cups of the remaining Cool Whip
. Tint remaining Cool Whip
with food colouring; spread on top of cake to resemble ice rink. Outline outside edge of rink with blue decorating gel. Refrigerate 1 hour.