Mash 1 cup of warm cooked pinto beans. Add 3/4 cup melted margarine or butter, 1 cup of cocoa powder, and 1 TB of vanilla. Mix in 2 pounds (usually 1 bag) of powdered sugar gradually. Add 1 cup of chopped nuts, if desired. Pres into a 9x13 nonstick or oiled pan, and store in the fridge.