Preheat oven to 350°F and spray a 9-inch loaf pan with cooking spray. (Preheat to 325°F for a glass or stoneware pan and add 10-15 minutes to the baking time.)
In a large bowl, whisk together the bananas, melted butter, maple syrup, brown sugar, eggs, and vanilla extract until well combined.
In another bowl, sift together the flour(s), baking soda, baking powder, salt, and 1 teaspoon cinnamon.
Fold the dry ingredients into the wet ingredients.
Add the oats, walnuts, and mini chocolate chips and stit until combined.
Pour the batter into the prepared loaf pan.
Mix together the sugar and 1/4 teaspoon cinnamon and sprinkle over the batter.
Bake at 350°F for 70-80 minutes. Check it at about 60 minutes and if it is browning too much on top, cover it with aluminum foil.It is done when a toothpick inserted into the center comes out nearly clean with only a few moist crumbs attached. If you have an instant-read thermometer, it should read about 205°F.
Cool in the pan on a rack for 15 minutes. Then remove the loaf from the pan and cool to room temperature.
Wrap tightly in plastic wrap. Store at room temperature for 2 to 3 days or in the refrigerator for up to 5 or 6 days. Can be frozen for up to two months.
This recipe has also been tested with:1/2 cup sweet rice flour + 1/2 cup brown rice flour + 1/2 cup potato starch + 1/4 cup sorghum flour + 1/4 cup tapioca flour + 1 teaspoon xanthan gumOR1 cup brown rice flour + 1/2 cup potato starch + 1/3 cup tapioca flour + 1 teaspoon xanthan gum