In advance: Prepare candy chest pieces. Melt and combine the Light Cocoa and White candy and make 2 candy plaques each in 9 x 13 in. and Non-Stick Jelly Roll pans, each 1/4 in. deep. Refrigerate until firm; unmold and turn over 9 x 13 in. plaques. Bring to room temperature and cut the Jelly Roll plaques into 2 in. wide strips, 2-9 in. and 2-13 in. long. Attach the strips to the backside of 9 x 13 in. plaques at inside edges, using melted candy to create 1 box for lid and 1 box to top cake and hold candy. For lid, ice the outside top and sides of one candy box using royal icing. Let dry.