Inspired by a photo I saw on the chocolate peanut butter gallery, I attempted my own version tonight:
Step 1. Make a graham cracker crust.
I actually ran out of graham crackers due to the recent Thanksgiving Day run on pumpkin pies, and substituted oatmeal biscuits instead. In a food processor, crumb biscuits with half a stick of melted butter. Add nuts or oatmeal if you want to seem slightly healthier. Bake in oven for approximately 10-15 minutes (or until dry and crispy.)
Step 2. Melt peanut butter.
FYI: Real, wholesome, organic peanut butter that you store in the fridge DOES NOT melt in the microwave. I learned this first hand - it tends to burn. Instead use Jiff or some other artificially sweetened variety that melts easily. Pour melted peanut butter over the crust.
Step 3. Mix up your favorite brownie mix - any recipe will do. Pour batter over melted peanut butter and bake as usual.
Let the brownies cool a bit before you slice them (as this can get messy otherwise.)