Preheat oven to 350°F
Grease an 8 x 12 inch baking pan
Add beans, eggs, coconut oil, cacao powder, coffee, salt, maple syrup, and baking powder to a blender and blend until a smooth brownie batter forms
In a large mixing bowl fold chocolate chunks and chopped walnuts into brownie batter
Transfer brownie batter to pan
Bake for 45 minutes or until center is cooked through. Let cool and top with coconut butter. Cut into squares and serve.