Preheat the oven to 350 degrees Fahrenheit (180 degrees Celsius). Line the mini muffin tin with paper liners and set aside.
Mash the bananas in a large bowl with a fork or potato masher. It's ok if a little lumpy.
225 grams bananas
Vigorously whisk the oil, egg, vinegar, and vanilla extract into the mashed bananas until well combined.
56 grams oil, 1 large egg, 1 teaspoon apple cider vinegar, 1 teaspoon vanilla extract
Add the flour, granulated sugar, baking powder, baking soda, salt, and cinnamon. Fold into the wet ingredients with a rubber spatula until the dry streaks of flour just disappear.
120 grams all purpose flour, 100 grams granulated sugar, ¼ teaspoon baking powder, ½ teaspoon baking soda, ½ teaspoon salt, 1 teaspoon ground cinnamon
Divide the muffin batter between the paper liners, filling each ½-3/4 full.
Sprinkle coarse sugar on top of the muffins if desired. Bake for 14-18 minutes or the muffin tops are golden brown and a toothpick inserted in the center comes out clean.
Remove the muffin pan from the oven. Let the mini muffins cool in the pan for 5-10 minutes, then transfer to a wire cooling rack.
Let cool completely and enjoy!
Notes
Use overripe bananas with lots of brown speckles for the sweetest, most flavorful muffins.Do not overmix. Fold in the dry ingredients until just combined.Storage: Store mini muffins in a single layer in an airtight container at room temperature for 3-4 days. Line the bottom with paper towel to keep them from getting soggy.Freezing: Freeze in a sealed container for up to 3 month. Thaw overnight in the refrigerator or on the counter for 1-2 hours before serving.