Preheat the oven to 425°F. Line a standard muffin tin with cupcake liners and set aside.
In a large bowl, stir the melted butter with the brown sugar until combined. Add the mashed bananas and vanilla extract and stir to incorporate. Add the flour, baking powder, baking soda, salt, and cinnamon and stir until just combined. Fold in the chocolate chips.
6 tablespoons unsalted butter, ⅔ cup (133g) light brown sugar, 1 ½ cups mashed banana, ½ teaspoon vanilla extract, 1 ¼ cups (185g) gluten free flour, 1 teaspoon baking powder, ¾ teaspoon baking soda, ¼ teaspoon fine sea salt, ¼ teaspoon cinnamon*, ¾ cup (128g) semisweet chocolate chips
Transfer the batter to the prepared muffin tin, filling each liner almost all the way up (about ¾ full). Bake for 5 minutes then, without taking the muffins out, reduce the oven temperature to 375°F and continue baking for another 15 minutes. The muffins should be golden brown in color.
Allow the muffins to cool in the tin completely before removing.
Notes
The cinnamon is optional but adds a nice touch of flavor.