To begin, preheat the oven to 375. Then, grease your mini muffin cups with non-stick spray or line them with paper liners. You can spray the paper liners with non-stick spray to keep the muffins from sticking to the liners.
In a large mixing bowl, mash the bananas until they are applesauce texture. Add the egg, greek yogurt, milk, vanilla, baking powder, cinnamon, almond flour, coconut flour, all purpose flour, and oat flour. Mix well until a thick batter forms.
Transfer the batter into 16-20 small muffin wells and bake in the oven for 25 minutes. Remove from the oven and allow them to cool completely before serving to your little one.