Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a large bowl, mix the rolled oats, baking powder, salt, and cinnamon.
In a separate bowl, mash the banana and whisk in the egg, honey (or maple syrup), and vanilla extract until smooth.
Combine the wet and dry ingredients, stirring until a thick dough forms. Fold in any optional add-ins.
Scoop small portions onto the baking sheet, flattening them slightly.
Bake for 12–15 minutes, or until golden brown.
Let cool for a few minutes before serving.