Preheat oven to 350°F.
Rinse beans thoroughly and shake off any excess water. Blend beans and one egg in a food processor until the mixture is completely smooth.
Melt the butter in a mixing bowl in the microwave. To the butter, add bean and egg mixture, the remaining two eggs, vanilla and baby prunes, and mix thoroughly. Add sugar, flour and cocoa to the bowl; stir to combine.
Bake in buttered 9x13 pan for approximately 30 minutes, or until a knife inserted in the center comes out clean.