Sweeter than lavender, violet-cassis extract gives this cake by Wendy Kromer amazing flavor. Add just one drop of floral extract to 1 cup of buttercream.
Divide each 8-inch cake layer in half horizontally. Set aside 4 of the cut layers for the Cherry Blossom Cake; 4 for the Violet Cassis Cake; and 4 for the Rose Petal Cake.
Set one of the cake layers onto an 8-inch cardboard round, spread about 2/3 to 3/4 cup of the violet-candy-and-cassis-flavored buttercream onto it, then top with the next cake layer. Place about 3/4 cup of the violet cassis buttercream into a piping bag fitted with a 1/2-inch diameter pastry tip, and pipe a ring of icing around the edge of the cake layer (this will act as a dam for the pastry cream); spread the vanilla pastry cream inside the piped buttercream ring. Top with the next layer and spread 2/3 to 3/4 cup of the violet cassis buttercream on top. Add the last layer, then spread the entire tier with the remaining violet-cassis buttercream. Chill the tier, then spread a final, smooth coat of buttercream and chill again. Make sure there are no bumps in the buttercream coating as they will be visible once the tier is covered with the rolled fondant. Cover this tier using the pale purple rolled fondant. Lay a stencil on the top of this tier, then smooth the corresponding colored royal icing over the stencil using a metal offset spatula. Smooth away the excess royal icing, and lift off the stencil.
Can't find cassis at your local spice shop? Kromer suggests perfumersapprentice.com.