Preheat the oven to 350℉ and line an 8x8” baking pan with parchment paper.
Pulverize 1 cup of the oats until finely ground. Transfer to a bowl and add the whole oats, baking powder, salt, and cinnamon and whisk to combine.
2 ¾ cups old-fashioned rolled oats, 1 teaspoon baking powder, ¾ teaspoon kosher salt, 1 teaspoon ground cinnamon
Add the bananas to a large mixing bowl and mash slightly with a fork, leaving chunks.
1 cup mashed bananas
Add the peanut butter and brown sugar and whisk to combine. Add the egg, vanilla, and whisk again, then add the milk and whisk until smooth.
⅔ cup peanut butter, ⅓ cup light brown sugar, 1 large egg, 2 teaspoons vanilla extract, ¾ cups milk
Add the oat mixture and use a rubber spatula or wooden spoon to mix until combined. Finally, mix in ¾ cup of the chocolate chips, saving the rest for the tops.
1 cup semi-sweet chocolate chips
Add the mixture to the prepared pan and spread evenly.
Bake for 25 minutes, sprinkling on the remaining chocolate chips at the 20-minute mark.
Remove to a wire rack to cool for one hour. Refrigerate for one additional hour, then slice and serve.