Make royal icing drop flowers one day in advance. Prepare royal icing following recipe directions. Tint dark violet; reserve a small portion white. Use tip 2D and dark violet icing to pipe 15 swirl drop flowers on parchment paper-covered cake board. Use tip 3 and white icing to pipe dot centers. Let dry overnight.
Make cake. Prepare batter following recipe directions. Bake and cool cake. Cake is three-layers. Trim one layer to 1 in. high for a 5 in. high tier. Place on foil-wrapped cake board, cut to fit.
Decorate cake. Prepare buttercream icing following recipe directions. Tint light violet. Use spatula and violet icing to ice cake smooth. Use tip 2D and light violet icing to cover cake sides and top with stars.
Position royal icing drop flowers on cake top. Use dots of icing to secure, if necessary.
One of the most popular techniques, stars come in a range of sizes and styles. Experiment with open and closed stars for variation in look. The star technique is timeless and can be used as a classic border or as a stunning fill-in for the top of a dessert.