Pre-heat oven to 350 degrees F. Line 8×8 baking pan with parchment.
In a large bowl, microwave safe bowl melt butter. Whisk for 30 seconds to cool.
Whisking rapidly, add beaten egg. Whisk until thick, about 30 seconds.
Add brown sugar, pumpkin, pumpkin spice, cinnamon, nut meg, all spice, and vanilla extract, whisk until combined.
Add flour and half of the chocolate chips, fold with spatula until ingredients come together.
Pour batter into prepared baking pan, top with remaining chocolate chips.
Bake 25-28 minutes or until tooth pick comes out with moist crumbs.
Let bars sit in pan to set and cool, lift sides to remove bars from pan.
Cut and serve.