In Advance: Cut out a large round cookie using Roll-Out Cookie recipe and largest circle cutter in 101 Cookie Cutter Set. Cut 1/4 section out of cookie. Bake and cool. Ice cookie smooth in white royal icing. Let set. Using tip 104, pipe ruffle on cut out edge. Let set.
Decorate in Order: 1. Ice cake top and sides smooth using white buttercream icing.
2. Cover top with tip 3 lattice in white buttercream icing.
3. Pipe tip 3 beads in white buttercream on top and middle edges.
4. Pipe tip 18 shell bottom border in white buttercream.
5. Add tip 3 beads on shell border in white buttercream.
6. Position cookie on cake top.