Here's what I did:
I actually used the Williams Sonoma Brownie Mix (posted in the "Taste This" Column- and they were delicious! I filled my cupcake tins half full with brownie mix and cooked them per the package directions. Then I let them completely cool, I scooped vanilla ice cream (per the birthday boy's request) and topped the ice cream with crunched chocolate cookies (the cat cookies from Trader Joe's). We added some sprinkles for festivities and then I popped them into the freezer to harden. I even made mini ones for the kids :) Take them out a few minutes before serving so they can soften just enough to pop them out of the tins, I had to use a butter knife to loosen them, but then came out fairly easily! Enjoy and thanks to JOY of BAKING for the great idea!!!