Makes about 20 servings.
Melt candy in disposable decorating bags following package instructions. Place mold on cookie sheet. Snip off end of bag and pipe candy into rick rack design of mold. Refrigerate until set. Carefully remove from mold. Repeat.
Bake and cool favorite 2-layer chocolate cake recipe in 8 in. square pan following recipe instructions. Stack and fill layers on foil-wrapped cake board. Spatula ice cake in chocolate buttercream icing.
Line cookie sheet with parchment paper. Measure and mark rectangle to match the size of your cake sides. Pipe marked line with melted cocoa candy; chill until set, about 5 minutes. Drizzle lines of various colors of melted candy inside cocoa candy outline; chill 5 minutes. Cover rectangle, including drizzled candy lines, with melted cocoa candy. Chill until set, about 20 minutes. For more stability, add a second layer of melted cocoa candy; chill until set. Carefully remove from parchment paper. Repeat for three additional plaques.
Attach candy plaques to sides of cake with chocolate buttercream icing. Zigzag corners of cake at plaque edges with tip 16 chocolate buttercream. Insert candy "candles" into top of cake.