It may sound odd but I was looking for this exact cake for a friend's birthday. He's not even in construction... long story. I hadn't thought of cereal bars! You've just made my life infinitely easier. Thanks!
mines a 12" square sponge cake for the base, and shaped cone, but you can cheat and use those chrispie bars, get loads of them and mix them together to make the cone shape, then cover with icing.....make it thicker than usual though so the finish is nice n smooth!! good luck!