Turn off the heat and slightly cool. When mixture is warm, add chocolate chips and stir until completely dissolved. At the end add rum, stir and set aside. Now you have everything needed to build the Porcupine body . Delicately loosen cake from aluminum foil but don't remove the foil.
Place stencils on top of cake.
Using a sharp knife cut the cake following the stencil edge. Remove left over cake to the bowl. With the cardboard under the cake it is easy to move. Add syrup for filing and blend until whole cake is equal in color and moist. If truffle paste is too dry, you may blend in a little of moistening syrup.