mugs. I fit 4 mugs inside of a 6 quart crockpot. Don't pick fancy-schmancy mugs--use the ones that you don't think twice about throwing in the dishwasher or heating up in the microwave.
your favorite brownie mix
the stuff your favorite brownie mix tells you to use
Mix up the brownie mix according to the directions listed on the package. I used the new gluten-free brownie mix from Trader Joe's. (psst. I did NOT spray the mugs first with cooking spray. You might want to. They're kind of a pain to clean.) Spoon brownie mix into each mug, filling it about 1/2 to 2/3 of the way. The brownie mix I used only makes an 8 x 8 pan, so each of my mugs were 1/2 filled. Put the mugs in the crockpot. Cover and cook on high for 1 1/2 to 3 hours. Our brownies were finished at 2 hours, 15 minutes (see note down below). You will know they are fully cooked when they have risen, pulled away at the sides and you can insert a knife and pull it back out clean. Unplug the crockpot, and let the mugs sit with the lid off. They will be TERRIBLY HOT. Don't get burnt. Leave them alone for a bit before removing. When the mug is coolish to the touch, top with whipped cream or vanilla ice cream.