1. Whisk GF flour, cornstarch, pumpkin pie spice, baking soda, and salt.
2. Melt butter and granulated sugar. Beat egg, vanilla, and pumpkin butter until foamy. Add butter mixture and beat well. Add GF flour mixture and beat until combined.
3. Add chocolate chips and mix. Pour the batter in pan. Scatter chocolate chips evenly over the top and press them gently into the batter. Bake.
4. Let bars cool. Slice, serve, and ENJOY!