Line an 8 x 8-inch pan or 9 x 4-inch loaf pan with parchment paper and set aside.
In a large bowl, combine the flours, protein powder and cocoa powder and mix well. Set aside.
In a microwave safe bowl or stovetop, combine the peanut butter and maple syrup and heat until melted. Pour the wet mixture into the dry and mix well. If the batter is too thick, slowly add milk, one tablespoon at a time, until thick.
Transfer to lined baking dish and press firmly into place. Refrigerate for at least 30 minutes, before drizzling with chocolate.
* Depending on the flour and protein powder combination, you might need more milk to firm up.