1. Preheat oven to 350°.
2. Weigh or lightly spoon flours and potato starch into dry measuring cups; level with a knife. Combine flours, potato starch, baking powder, xanthan gum, and salt in a medium bowl; stir with a whisk.
3. Combine brown sugar, melted butter, and oil in a medium bowl; stir with a whisk until blended. Add vanilla and eggs, stirring with whisk until blended. Gradually add flour mixture, stirring until blended. Fold in minichips, brickle chips, and pecans.
4. Pour batter into an 8-inch square metal baking pan coated with cooking spray. Bake at 350° for 20 minutes or until a wooden pick inserted in center comes out clean. Cool completely in pan on a wire rack.