Preheat oven to 425° F. Line and spray a 12 cup muffin tin with nonstick cooking spray.
In a large bowl whisk together the gluten free flour, cocoa powder, brown sugar, baking soda, cornstarch and salt and set aside.
To a blender, add the bananas, honey, melted chocolate, vanilla, coconut oil,and greek yogurt. Blend on high until smooth and creamy, about 30 seconds. Add the eggs and blend again until smooth. Pour the wet ingredients into dry ingredients and whisk until just combined. Gently fold in both types of chocolate chips, saving a few to top the muffins.
Divide batter evenly into muffin tins, filling just under all the way full. Place a few reserved chocolate chips on top of each muffin. Bake for 5 minutes at 425° then reduce heat to 350° and bake for an additional 13-15 minutes or until tooth pick comes out clean or with just a few moist crumbs attached. Cool muffins in the muffin pan for 5 minutes then transfer to wire rack to cool completely. Keep in an air tight container at room temperature for 3 days or in the freezer for up to one month. Muffins are best served warm!