Preheat oven to 350 degrees F.
Line a 12-cup muffin pan with paper liners or spray with cooking spray.
In a medium bowl, whisk together sweet rice flour, millet flour, coconut flour, baking powder, baking soda and salt. Set aside.
In another medium bowl whisk together the melted and cooled butter, sugar, eggs, mashed banana and vanilla. Be sure to mash the banana well with a fork - no chunky banana bites!
Use an ice cream scoop to evenly divide batter into muffin tins. Add a few more chocolate chips on top of each one. Bake for about 25 minutes or until a toothpick inserted comes out clean.
Store on the counter in an airtight container for up to four days or freeze.