Preheat the oven to 350°F (175°C). Thoroughly coat the bottom and sides of a 9 × 13-inch baking pan with nonstick cooking spray or a small amount of butter.
Place the melted butter and chopped unsweetened chocolate in a medium saucepan over low heat. Stir frequently until the chocolate has fully melted and the mixture is smooth.
Remove the saucepan from the heat. Stir in the cocoa powder, granulated sugar, and kosher salt until evenly incorporated, then mix in the vanilla extract.
Add the three eggs individually, stirring briskly after each addition so they blend into the warm chocolate mixture without beginning to cook.
Gently fold in the all-purpose flour just until a thick, glossy brownie batter forms.
Transfer approximately three-quarters of the brownie batter to the prepared pan. Spread it into a level layer with a spatula, then reserve the remaining batter—about 1 cup—for the marbled topping.
In a large mixing bowl, beat the softened cream cheese with an electric mixer until completely smooth.
Add the granulated sugar, cinnamon, ginger, cloves, and kosher salt. Continue beating until evenly blended, pausing to scrape the bottom and sides of the bowl when necessary.
Beat in the two eggs one at a time, mixing thoroughly after each addition.
Add the pumpkin purée, heavy cream, and vanilla extract. Beat until the cheesecake mixture is creamy, uniform, and free of visible lumps.
Pour the pumpkin cheesecake batter over the brownie layer and spread it evenly across the pan.
Drop spoonfuls of the reserved brownie batter over the pumpkin layer. Draw a dull knife gently through both mixtures to create a pronounced marbled pattern. Avoid excessive swirling so the chocolate and pumpkin streaks remain distinct.
Bake for 40 to 45 minutes, or until a toothpick inserted near the center comes out clean.
Place the pan on a wire cooling rack and leave the brownies inside the pan until completely cool.
Once fully cooled, slice the dessert into 24 evenly sized squares.