Preheat oven to 350°F (180°C) and prepare a muffin mold with muffin liners. Make sure you grease the liners to prevent the muffins from sticking.
In a large bowl, mash the bananas then combine with egg, Greek yogurt, maple syrup, vanilla extract, cinnamon and a pinch of salt. Stir well until you get a smooth mixture.
Add into the wet mixture oat flour, almond flour and baking powder. Stir the ingredients together while pouring in the milk gradually. Start mixing until the batter reaches a smooth consistency free of lumps.
Mix in any extra such as chocolate chips, if desired.
Fill ⅔ of each muffin liner with the batter, sprinkle with chocolate chips (optional) and bake in hot oven for 20 to 25 minutes. Make sure you do not overbake the muffins; they are ready when a toothpick inserted into the center comes out clean.
Remove your banana muffins from the oven and let cool over a baking rack for at least 15 minutes.