1Heat oven to 350°F. Spray 16 regular-size muffin cups with cooking spray (without flour).
2In small bowl, mix flours, xanthan gum, baking powder, baking soda and salt with whisk; set aside. In medium bowl, beat eggs, oil, milk, bananas, brown sugar and vanilla with electric mixer on medium speed until well blended. Gradually add flour mixture, beating until well blended. Stir in chocolate chips. Divide batter evenly among muffin cups, filling each about three-fourths full.
3Bake 18 to 20 minutes or until toothpick inserted in center comes out clean. Cool 5 minutes; remove from pan to cooling rack. Serve warm.