Bake White Chocolate Layer Cake in three 6 in. round baking pans. Cool layers completely. Stack cooled layers on foil wrapped cake circle, spreading chocolate icing between layers. Place on dessert plate, if using.
Cut strip of parchment paper 2-3 in. higher than your cake and long enough to fit around cake with at least an inch extra (approx. 8½ x 21½ in). Melt about 1/2 package each of white and dark cocoa Candy Melts in disposable decorating bags. Drizzle randomly over prepared parchment paper. Let stand at room temperature until set (shine will be gone but candy will still be pliable; should be able to touch candy without it sticking to your finger.) Wrap around iced cake, pressing lightly onto the sides. Refrigerate until candy is firm, about 10 minutes.
Carefully remove parchment paper. Add raspberries, if desired, to garnish.