Preheat your oven to 175°C (350°F). Line a baking pan with parchment paper, leaving overhang for easy removal.
Peel and mash the ripe bananas in a large bowl until smooth, with no large lumps remaining. The mixture should smell sweet and fragrant.
Add the honey, nut butter, and vanilla extract to the mashed bananas. Stir everything together until the mixture is well combined and slightly sticky.
Stir in the toasted rolled oats and baking powder, mixing until the dry ingredients are evenly incorporated. The batter will be thick and sticky.
If desired, fold in chocolate chips, nuts, or dried fruit for extra flavor and texture.
Spoon the mixture into the prepared pan. Use the back of a spatula to press it evenly into the corners, about 1.5 inches thick. Press firmly to ensure the mixture is compact.
Bake in the preheated oven for 20-25 minutes, until the top turns a light golden brown and starts to crack slightly.
Remove the pan from the oven and let the bars cool in the pan for about 10 minutes. They will firm up as they cool.
Using the parchment overhang, lift the entire block out of the pan and place on a wire rack. Slice into squares or rectangles, about 1 inch thick.
Let the bars cool completely before serving. They should be chewy with a rustic appearance, featuring a lightly cracked top and a golden hue.
