1 box brownie mix
1 can black beans
Dump the brownie mix into a bowl. Pour the liquid out of the can of beans and fill can with water (with the beans still in the can, too) Dump the beans & water into a food processor and process until there are very few specks left. Dump bean mixture into bowl with brownie mix and stir until combined. Follow directions on the brownie mix box for pan size and baking temperature and time.
This was an interesting recipe- an experiment, really. There's definitely no perceptible "bean" taste, but the texture is affected. The first day, they were fudgy and sticky, and my husband described them as "light" tasting. The following days, they became more chewy and their stickiness subsided. On day three, a coworker described them as tasting "old", but he couldn't bee more specific. I'd say they were a bit spongy, maybe? They were definitely good the first day, and only marginal the following days. But, then, who turns down a marginal brownie? Chocolate is chocolate.
On the upside, these are the healthiest brownies I've ever made- I used a low-fat mix in addition to the beans.