Using the black, chocolate flavoured batter, pipe your design onto the parchment paper, tracing the drawing that you've already prepared.
Fill in the shape of the ghost outlines with the plain batter from the other piping bag.
Transfer the whole pan to the freezer to firm up for about 10 minutes. Meanwhile, start pre-heating your oven to 350°F.
Take the pan out of the freezer, and carefully remove your paper drawing out from under the parchment paper.
Pour the orange batter on top of your piped design. Spread the batter evenly across the pan, taking care not to disrupt the design below. The batter will not settle or flatten on its own, so try to get it as smooth and as even as possible.
Bake for 12-14 minutes until the cake is springy, and is just barely starting to brown at the edges.
Lay a clean tea towel onto your counter top and generously dust it with icing sugar.
When the cake comes out the oven, lay a fresh sheet of parchment on top, and place a cooling rack, upside down, on top of the parchment. Flip the whole tray over so the cake is now resting on the cooling rack with the design face up.
Carefully peel the parchment paper off the top of the cake (the side with the design).
Flip the cake again, so the design is facing down, onto the sugar dusted tea towel.
Roll the cake and tea towel up together to form a log. Set aside and allow the cake to cool completely, still wrapped, for at least an hour. Once the cake has cooled, you can start on the filling.