Preheat the oven to 350℉/180℃. Grease an 8×8 inch square pan. For easy removal of the brownies, place parchment paper on the bottom and 2 sides of the pan. Grease again and then set side.
Before starting, spread the pumpkin puree onto a plate and blot it with paper towel sheets to remove any excess liquid. Do this twice and set aside.
1 cup pumpkin puree
In a large bowl, add butter, dark brown sugar, and white sugar. Cream together for 2-3 minutes or until well combined. I recommend using a handheld electric mixer for this.
1/2 cup butter, 1/2 cup dark brown sugar, 1/2 cup white sugar
Add in egg yolk, vanilla, and blotted pumpkin puree. Continue mixing for another 1-2 minutes until smooth.
1 egg yolk, 1 tbsp vanilla
Add in flour, baking soda, cinnamon, allspice, ginger, and salt. Slowly mix in using a spatula until no flour streaks appear. Do not overmix!
2 cups all-purpose flour, 1 tsp baking soda, 1 1/2 tsps cinnamon, 1/4 tsp allspice, 1/4 tsp ginger, 1/4 tsp salt
Toss in the chocolate chips and mix in a few times.
1 cup semi-sweet chocolate chips
Transfer into the prepared pan and spread out evenly. Add more chocolate chips on top if desired. Bake the bars for 25-30 minutes. A toothpick inserted should come out with a few moist crumbs on it. If it is wet, it isn't ready yet. Continue to bake at 5 minute intervals until the edges are set.
Remove the pan from the oven and cool the bars on a wire rack before cutting into squares.