Preheat oven to 350°F. Grease 8x8x2-inch pan with nonstick cooking spray.

In small bowl, whisk together brown rice flour, potato starch, baking powder, and salt. Set aside. In large bowl, cream together butter, peanut butter, and sugars until light and fluffy, about one minute. Add eggs, one at a time, and beat well between each addition. Stop mixer and scrape down bottom and sides of bowl. Turn mixer back on and continue to beat until mixture is light, fluffy, and almost white. Turn off mixer. Add dry ingredients, turn mixer to low and blend to combine. Add chocolate chips. Mix until just combined.

Spread batter evenly into prepared pan. Bake until bars are puffy, golden brown, and a cake tester interested into the center of the bars comes out with a few moist crumbs, about 35 minutes. Place pan on wire rack to cool. When cooled, cut into 12 bars.