I can't claim any credit for this one; I first heard about it from a friend, and have seen some versions around the web (such as this excellent tutorial by Ree, http://thepioneerwoman.com/cooking/2010/03/a-blast-from-the-past/ ). Still, I can say it's a great deal of fun, and works marvelously well as a surprise for dinner guests.
I ended up mixing and matching actual flower pots and handle-less teacups; until I started the project, I didn't realize just how many flowerpots of mine had drainage holes in the bottom, which did not seem particularly ice cream friendly. On the other hand, I discovered that this is an excellent way to get rid of extra cake scrids: jigsaw them together at the bottom of the pot. If it's chocolate cake, crumble it over the top for crumbs, too!
Thinking happy spring thoughts to everyone!