For the tall part, I actually used a round glass pyrex dish with slanted sides and then cut the edges off and stacked them on the main piece...doubling the height. It was touch and go for a bit, but the icing holds it all together, so it looks cool, and I get the perfect divet in the top of the hat to boot!

EDIT: So the cake itself is four pieces: the base, the bottom of the hat, and then the top of the hat is in two pieces...all of it stuck together with icing.

I am not sure that makes sense...