In a food processor, process the black beans until they are mostly broken up. Add the peanut butter and agave syrup to a microwave-safe bowl and microwave for 30-45 seconds, until the peanut butter is melted but not boiling hot. Add the melted peanut butter, agave, and the cocoa powder to the food processor and continue to blend until you have a smooth mixture.
Transfer to a bowl and gently stir in the crushed nuts.
Line a 9 x 9 inch pan with plastic wrap and spray with non-stick spray. Press the brownie mixture into the pan and smooth out the top. Cover and refrigerate for at least an hour or overnight. Slice into 9 brownies.