Preheat oven to 350.Make a flax egg by combining 1 tbs of flax meal with 3 tbs. water. Allow to sit for 5 minutes.Mash banana in a large bowl.Add protein powder, coconut flour, cocoa powder, stevia, peanut flour, almond meal, coconut oil, vanilla, salt, and oat flour and flax egg to the mashed bananas and stir to fully incorporate.Add baking powder and baking soda and stir to combine.Grease a mini loaf pan and add ½ of the batter to the pan.Spread a layer of peanut butter over the batter. Cover the peanut butter with coconut sugar.Add the remaining batter and smooth out the top.Bake for 40 minutes at 350F.