Preheat your oven to 350°F (175°C) and grease a 9x9-inch baking pan.
In a large bowl, whisk together the pumpkin puree, granulated sugar, brown sugar, and melted butter.
Add the eggs and vanilla extract to the mixture, whisking until smooth.
In a separate bowl, combine the flour, cocoa powder, baking powder, salt, cinnamon, and nutmeg.
Gradually fold the dry ingredients into the wet mixture, stirring until just combined.
Gently fold in the chocolate chips.
Pour half of the brownie batter into the prepared pan and spread evenly.
Spoon the pumpkin mixture on top of the brownie base, spreading it evenly.
Top with the remaining brownie batter and swirl gently for a marbled effect.
Bake for 30-35 minutes, or until a toothpick inserted in the center comes out clean.