Prep the pan and oven. Heat the oven to 350°F (175°C). Line an 8x8-inch baking pan with parchment, leaving a bit of overhang for easy lifting. Lightly grease the parchment.

Mash the bananas. In a large bowl, mash the bananas until mostly smooth with a few small lumps. You should have about 1 to 1 1/4 cups of mashed banana.

Whisk in the wet ingredients. Add the egg, honey, oil, and vanilla. Whisk until combined. Taste the mixture—if your bananas aren’t very sweet, add another tablespoon of honey.

Stir in the dry ingredients. Add oats, cinnamon, baking powder, and salt. Fold until the oats are evenly coated and the batter is thick and scoopable.

Add mix-ins. If using chocolate chips, nuts, or dried fruit, fold them in now. Keep total add-ins to about 1/2 cup so the bars hold together well.

Spread and level. Transfer the batter to the pan. Use a spatula to press it firmly and evenly into the corners. Compacting helps the bars slice cleanly.

Bake. Bake for 22–28 minutes, until the top is set and lightly golden around the edges. A toothpick should come out with a few moist crumbs but not wet batter.

Cool completely. Let the pan cool on a rack for at least 30–45 minutes. Lift out using the parchment and cool another 10 minutes before slicing into 12 bars.

Optional finish. Drizzle a little warm honey over the cooled bars or sprinkle with a pinch of flaky salt for contrast.