1. Get Ready: Preheat your oven to 350°F (175°C). Lightly grease an 8x8-inch baking dish with a little butter or cooking spray.
2. Wet Mix: In a big mixing bowl, whisk together the peanut butter, maple syrup, milk, eggs, vanilla extract, and mashed banana until everything looks smooth and well combined.
3. Dry Mix: In a separate bowl, combine the oats, cocoa powder, chocolate protein powder (if using), baking powder, and salt. Give it a good stir.
4. Combine: Slowly add the dry oat mixture to the wet ingredients, stirring gently until just combined. Be careful not to overmix!
5. Chocolate Time: Fold in most of the dark chocolate chips, saving a small handful to sprinkle on top if you like.
6. Bake It: Pour the oatmeal batter into your prepared baking dish, spreading it out evenly. Sprinkle the reserved chocolate chips over the top.
7. Golden Goodness: Bake for 30 to 35 minutes, or until the top is golden and set. You can check by inserting a toothpick into the center; it should come out clean.
8. Cool & Serve: Let the baked oatmeal cool for a few minutes before slicing into squares. Enjoy it warm, or even chilled for a refreshing summer breakfast! A little extra drizzle of peanut butter makes it extra special.