1-Preheat the oven to 350°F (175°C): Preheat the oven to 350°F (175°C). Line a standard muffin pan with 6 paper liners and lightly grease them with cooking spray. (This recipe makes 6 oatmeal cups, but it can easily be doubled.)
2-In a mixing bowl, add the banana: In a mixing bowl, add the banana and mash it well with a fork until mostly smooth. Add the egg, peanut butter, honey (or maple syrup), milk, and vanilla. Whisk until everything is well combined.
3-Add the rolled oats, baking powder, salt,: Add the rolled oats, baking powder, salt, and cinnamon. Stir until the batter is evenly mixed. Finally, fold in the chocolate chips.
4-Divide the batter evenly among the prepared: Divide the batter evenly among the prepared muffin cups, filling them almost to the top. Sprinkle a few extra chocolate chips on top if desired.
5-Bake for 20-25 minutes, or until the: Bake for 20-25 minutes, or until the oatmeal cups are set and lightly golden. Let cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.
6-Store in an air-tight container up to: Store in an air-tight container up to 5 days.