Preheat your oven to 350°F (175°C) and prepare a 9x9 inch baking pan by lining it with parchment paper.

In a large mixing bowl, beat together the cream cheese, granulated sugar, and cornstarch until smooth and creamy (about 2-3 minutes). Mix in the pumpkin puree, sour cream, vanilla extract, and pumpkin pie spice until fully combined.

Add the eggs to the pumpkin cheesecake mixture one at a time, blending well after each addition on medium speed for about 1 minute. Set aside.

In a separate bowl, whisk together the all-purpose flour, Dutch process cocoa powder, and salt until well combined.

Melt the unsalted butter and semi-sweet chocolate over low heat in a medium saucepan, stirring until smooth and glossy (about 3-5 minutes). Let cool slightly.

In a large mixing bowl, beat together the eggs, granulated sugar, and vanilla extract until pale and thick (about 3-4 minutes). Fold in the slightly cooled melted butter and chocolate.

Carefully add the dry ingredient mixture to the wet chocolate batter, folding until just combined.

Pour half of the brownie batter into the prepared pan. Spread the pumpkin cheesecake filling over the brownie base. Dollop the remaining brownie batter on top and swirl with a knife.

Bake for 52-55 minutes until the center jiggles but the edges are set. Let cool in the pan for at least 30 minutes.

Transfer the brownies to the fridge to chill for at least 6 hours before slicing into squares.