In a large bowl, stir together the oil, eggs, and mashed bananas. Stir in the gluten free flour, sugar, baking powder, baking soda, salt, and cinnamon until combined.
Fold in the chopped chocolate, then divide the batter evenly between the muffin cups, filling each one about ⅔ full. Preheat the oven to 375°F and rest the batter while the oven heats.
Bake the muffins for 20 to 24 minutes, until a tester comes out mostly clean ( (a few moist crumbs are OK).
Remove the pan from the oven, let the muffins rest for 5 minutes in the pan, then turn them out onto a rack to cool completely. Muffins are great warm or at room temperature.
Notes
Fill the muffin cups ⅔ full for this recipe – While some muffin recipes advise filling the muffin cups to the brim, I’ve found that about ⅔ full is the sweet spot so that they rise nicely but don’t overflow the cups.
Always rest the batter. Gluten-free flour blends, especially a blend that contains rice flour, needs to hydrate before its baked for the best results. Let the batter rest in the muffin tin for 20 minutes, or for at least as long as it takes to heat the oven.
Adjust the sweetness - Bananas are very sweet on their own, and the riper they are the sweeter they'll be. You can reduce the sugar ½ cup or use ½ cup of maple syrup instead of the granulated sugar.
Make them into pumpkin muffins - Swap 1 cup of applesauce for the mashed bananas (or just make my oat flour pumpkin muffins).
Egg-free - Omit the egg to make these muffins vegan. They will be denser but the bananas will work as a nice binder even without eggs.