Prep the oven and pan: Preheat to 350°F (175°C). Line a baking sheet with parchment paper or a silicone mat.
Mash the bananas: In a large bowl, mash bananas until mostly smooth with a few small lumps.
Add wet ingredients: Stir in peanut butter, honey or maple syrup (if using), egg, and vanilla until well combined.
Combine dry ingredients: Add oats, cinnamon, baking powder, and salt.
Stir until the mixture is thick and evenly moistened.
Fold in mix-ins: Gently stir in your chosen add-ins, keeping the total to about 1 cup so the cookies hold together.
Scoop the dough: Use a heaping tablespoon or a 2-tablespoon cookie scoop to portion onto the baking sheet. Flatten slightly with damp fingers; these don’t spread much.
Bake: Bake for 12–15 minutes, until the edges are set and lightly golden. The centers should feel firm but still soft.
Cool: Let the cookies cool on the pan for 5 minutes, then transfer to a wire rack to cool completely.