Yes, I know I already did this month's challenge, but I couldn't decide and these were too perfect to make for a Packer party this past weekend.
Here's the recipe (although I'd originally found it on a different site, the link to which I cannot find now): Mint Filled Brownie Cupcakes (from Martha Stewart Cupcakes).
My only change was to top it with Peppermint Buttercream (I have no idea the amount of anything - 1 1/2 sticks of unsalted butter to god knows how much powdered sugar + ~3/4 t peppermint extract and lots of green food coloring and a little milk? LOL)

YUM. These are already on my list to be made for my ILs' big NYE party (except I'm going to make them in mini cupcake form because the big cupcakes were DELISH, but were best suited to eating with a fork, not unwrapping and popping while you're standing around chatting. So I'm going to try and find York mini-balls and do that instead.)
The "heaping tablespoon" you're supposed to put into the liners first? The amount was WAY off... my patties wound up pretty near the top and seeped out a little. So next time I'll use a little less on the bottom to get the York patty (or ball) more toward the middle.
The brownie overall was ONE OF, if not THE BEST, brownies I've ever had. Considering how easy it was, these will be made and toyed with repeatedly (I can already see caramel filled balls, peanut butter balls, etc.) I think I even made a batch of cookies while the chocolate was melting on the stove.
Re: December Cooking Challenge: Mint Filled Brownie Cupcakes
That's hard to say. I mean, you definitely taste some mint (especially with the mint buttercream on top.) But it wasn't nothing BUT mint - I'm not sure anything could completely overpower the yummy gooey chocolatey goodness that is the brownie.