Make 4 3/4 cups of buttercream icing: Tint 2 1/4 cups light rose (thin with 2 tablespoons light corn syrup). Tint 3/4 cup dark rose. Tint 1/4 cup green. Reserve 1 1/2 cups white.
Bake and cool 2-layer cake (bake two 1 1/2 in. high layers to make a 3 in. high cake). Ice smooth in light rose. Mark 1 1/2 in. from top edge and trace heart shape for lattice with toothpick. Pipe tip 5 lattice heart. Pipe tip 18 rosettes in dark rose around edge of lattice. Add tip 352 leaves. Pipe tip 21 shell bottom border. Add tip 3 dots.
The rosette has the tight, swirling look of a rose, but is achieved in one continuous rotation, rather than with wrapped layers of petals. Single rosettes are also used as candleholders on top of a cupcake.