Preheat oven to 350 F. Combine all ingredients except chips in a good food processor, and blend until completely smooth. Really blend well. (A blender can work if you absolutely must, but the texture—and even the taste—will be much better in a food processor.).
Stir in the chips, then pour into a greased 8×8 pan.
Optional: sprinkle extra chocolate chips over the top.
Cook the black bean brownies 15-18 minutes, then let cool at least 10 minutes before trying to cut. If they still look a bit undercooked, you can place them in the fridge overnight and they will magically firm up!