Chocolate or vanilla icing
Pop Rocks (which you can rename “Fire crystals” throughout the party)
Prepare and cook the cake mix per the package instructions, though placing them in muffin cups.
Once the cakes cooled a bit, add frosting using a cookie scoop. Try to have the icing looking as though smoke or steam is coming out of the cauldron.
Cut the licorice into small pieces and poke both ends inside the cakes, to make the cauldron handle.
Sprinkle with “Fire Crystals”.