Make rosebuds 1 day in advance. Prepare royal icing following recipe directions. Tint five different shades of red. Use tip 104, cut disposable decorating bags and tinted icing, pipe rosebuds: three lightest red, 10 light red, 15 medium red, 20 dark red and 24 darkest red. Let dry overnight on parchment paper-covered cake board.
Make cake. Prepare batter following recipe directions Bake and cool cake. Prepare chocolate buttercream following recipe directions. Torte, stack and fill for a 3-layer, 6 in. high cake.
Decorate cake. Use spatula and chocolate icing to ice cake smooth. Add five rows of rosebuds on top of cake, starting on the outer edge of the cake with darkest red and working inward to the lightest red.