For the brownie filling, in a medium saucepan melt together the butter, chocolate chips, and brown sugar over medium heat just until melted. Remove from heat and allow to cool for 10 minutes. Whisk in the eggs one at a time. Mix together the remaining dry ingredients, then add into the mixture.
Pour half of the mixture in a greased a 9-10" spring form pan, and bake at 350°F for 20 minutes until the center is just set. Set aside the remaining batter.
For the pumpkin filling, in a large bowl combine all the ingredients, mixing until smooth.
Pour the pumpkin mixture over the warm brownie base. Add 1 Tbsp of water into the remaining brownie batter to loosen it a bit. Using a tablespoon, randomly dollop the remaining brownie batter onto the pumpkin filling.
Use the back of a spoon or a knife to pull the brownie batter around to create swirl patterns - do not over mix it. Bake for 40-45 minutes or until pie is set.
Cool for 10 minutes then run a sharp knife around the outer edge of the pan to release the pie from the edge to prevent the pie from cracking. Allow to cool completely before releasing pan ring.
Serve with ice cream or whipped cream if desired.