Preheat and prep: Heat the oven to 350°F (175°C).
Line a baking sheet with parchment paper for easy cleanup.
Mash and mix wet ingredients: In a large bowl, mash the bananas until mostly smooth. Stir in the peanut butter, maple syrup, and vanilla until creamy.
Combine dry ingredients: In a separate bowl, whisk the oats, oat flour, baking powder, baking soda, cinnamon, and salt.
Bring it together: Add the dry mixture to the wet mixture. Stir with a spatula until you get a thick, sticky dough.
If it feels crumbly, add 1–2 tablespoons plant milk. If it feels too loose, add a spoonful of oat flour.
Add the extras: Fold in your chosen add-ins. Keep it around 1/2 cup so the cookies hold together well.
Scoop and shape: Use a cookie scoop or a heaping tablespoon to portion onto the baking sheet.
Flatten each mound slightly with damp fingers; these cookies won’t spread much.
Bake: Bake for 11–14 minutes, until the edges are set and the tops look dry. They should be soft but not wet in the center.
Cool: Let the cookies rest on the sheet for 5 minutes, then move to a rack to cool completely. They firm up as they cool.
Taste and adjust next time: If you want them sweeter or softer next round, note your preferences now while it’s fresh.