Preheat oven to 350º /180ºC.

In a food processor or blender add beans, 2 eggs and vanilla, pulse several times until beans are broken up. Add 1/2 cup of cocoa powder blend until smooth and no lumps remain.

In a large bowl, cream the butter, sugar and salt. Add remaining egg and mix well. Add bean mixture. Stir until well incorporated.

Grease an 8×8 square baking dish. Pour in batter, tapping lightly to remove any bubbles. Bake for 35-45 minutes, or until toothpick inserted into center of brownie comes out clean.

Allow brownie to cool to room temperature. In a large bowl add brownie and crumble. Chill for 1 hour.

Line a cookie sheet with parchment paper. Once brownie crumble is firm, remove from fridge and form into 1 inch balls, place on cookie sheet and chill for 15 minutes.

In a large bowl add remaining ¼ cup of cocoa powder. One at a time roll chilled truffles in cocoa powder, tapping off any excess. Serve on a platter or store in an airtight container, separating the layers with parchment.