Decorate cakes. Fill one decorating bag with tip 1A with buttercream icing. Fill a second bag with a coupler and tip 8 with buttercream icing. Attach one decorated house piece to top of 6 in. cake. On cake sides, attach house pieces to sides of cake with icing. Pipe tip 8 bead trees. Pipe tip 1A snow mounds on cake tops and around bottom of houses, using spatula to form drifts. Pipe tip 2 dots on tiers.