Preheat oven to 180C/160C fan/350F.
Lightly oil a square baking dish, then add the bananas and mash with the back of your fork. Add the peanut butter and milk and mix to combine.
Fold in the oats, protein powder, baking powder and a pinch of salt. Give it a taste to make sure the sweetness is to your liking. If not, you have the option of adding 1-2 tablespoons of maple syrup or honey.
Top with a few more dollops of peanut butter and swirl it around with a sharp knife or skewer. Sprinkle the chocolate chips on top and bake for 35-40 minutes.
Serve warm or cold on its own, or with a dollop of yoghurt and berries/fruit.
