My nephew wanted a volcano cake. I made it extra special by having it actually explode. The cake is the wondermold covered in fondant. Before applying the fondant place a large test tube in the center of the cake. Put the fondant over the cake and then cut a small slit around the top of the test tube. When it comes time to light the cake, light the candles and then lift the top of the fondant, add diet coke to the test tube and then drop in 4 mint mentos. Your birthday kid will love it! Be sure to test the 'explosion' ahead of time so that you know how many towels to put under the cake. Or - We had the explosion outside to keep the mess out of the house.