Preheat the oven to 350 °F (180 °C). Line a 9-inch square pan with parchment paper. Slightly oil the pan with cooking spray. Set aside.
Mash the ripe banana, pack in measuring cups to get exactly 2 cups.
Place the mashed bananas in a mixing bowl, add peanut butter, oats, and chocolate chips and stir very well until it's consistently combined and thick.
Pour on the prepared baking pan, press evenly, and sprinkle extra chocolate chips on top if desired.
Bake the oats for 30-40 minutes at 350 °F (180 °C) until dry and golden on top and set.
Let the pan cool down for 15 minutes then lift the overhanging pieces of parchment paper to release the oats onto a cooling rack.
Let it cool down completely for 2-3 hours before slicing.
Slice and serve on a plate for breakfast with fruits, yogurt or plain.
