Preheat oven to 425°F (218°C). Spray a 12-count muffin pan with nonstick spray or line with cupcake liners. (If you need a recommendation, this muffin pan and this muffin pan have both held up well with very regular use.) Set aside.

In a large bowl, whisk the flour, baking soda, baking powder, cinnamon, and salt together. Set aside.

In a medium bowl, mash the bananas with a fork. Once mashed, whisk in the brown sugar, honey/maple syrup, coconut oil, egg, vanilla, and milk until combined.

Pour the wet ingredients into the dry ingredients and whisk until everything is just combined. Fold in the blueberries. Expect a semi-thick batter. Spoon the batter evenly into the muffin cups, filling them all the way to the top.

Bake for 5 minutes at 425°F (218°C); then, keeping the muffins in the oven, reduce heat to 350°F (177°C) and continue baking for another 15–18 minutes or until a toothpick inserted in the center comes out clean. The total time these muffins take in the oven is about 20–23 minutes, give or take. (For mini or jumbo muffins, see Notes for baking instructions.)

Allow the muffins to cool for 5 minutes in the muffin pan, and then transfer to a wire rack to continue cooling.

Muffins stay fresh covered at room temperature for a few days, or in the refrigerator for up to 1 week.