Prep your pan and oven: Heat oven to 375°F (190°C).
Grease a 24-cup mini muffin tin or line with mini liners.
Mash bananas: In a large bowl, mash the ripe bananas until mostly smooth. A few small lumps are fine.
Whisk in wet ingredients: Add the egg, yogurt, oil, vanilla, and maple syrup or honey. Whisk until well combined.
Add dry ingredients: Sprinkle flour, oats, baking powder, baking soda, cinnamon, and salt over the wet mixture.
Stir gently with a spatula just until no dry streaks remain.
Fold in blueberries: Toss blueberries with a teaspoon of flour if you like, then fold into the batter. Don’t overmix.
Fill the cups: Divide the batter among the mini muffin cups, filling each about 3/4 full.
Bake: Bake 10–13 minutes, until the tops spring back when touched and a toothpick comes out clean or with a few moist crumbs.
Cool: Let muffins cool in the pan for 5 minutes, then move to a rack to cool completely. This helps them set and stay tender.