Combine first 7 ingredients in a large bowl and mix well. (For a completely smooth batter you could use a blender but I just mash everything with a fork.) Add baking powder and protein powder and stir until well combined. Pour into a greased 9x9 baking pan (line the bottom with parchment paper for easy removal). Bake at 375 degrees for 13-15 minutes. Let cool, slice into 8 bars and drizzle with chocolate if desired.