1 box white cake mix
1 intense orange/dark chocolate candy bar
1 tub vanilla frosting
1 tub chocolate frosting
Follow instructions on cake box, but substitute orange juice for the water with exact same amount. Shave some of the chocolate bar into the batter. Bake according to package directions. Cool cupcakes.
Shave more chocolate bar into each of the tubs of frostings and add just a splash of orange juice into the white frosting. Spoon the white frosting into the decorator bag as it's laying on the counter (so it kind of fills it sideways) Next, spoon the chocolate frosting into other side of the decorator bag. Twist the top of the bag and pipe onto cupcakes as usual. This should create a "marbled" effect. Shave more chocolate bar onto the top of the cupcake and grate some orange zest onto the top of the cupcake.