Preheat the oven to 320°F/160°C. Line a 9-inch square baking pan with parchment paper or spray with non-stick cooking spray. Set aside.
Use a mixer to beat the cream cheese and granulated sugar together until fluffy and well combined.
Add the pumpkin puree, egg, ground cinnamon, and ground nutmeg. Beat until just combined. Set aside.
To make the brownie batter, place the butter and dark chocolate in a large heat proof mixing bowl. Bring a saucepan partially filled with water to a simmer over a low heat. Place the mixing bowl on top of the saucepan and stir the butter and chocolate until just melted. Remove from heat.
Mix the brown sugar, eggs, and vanilla extract into the chocolate mixture.
Stir through the flour and cocoa powder until just combined.
Spoon the brownie batter and pumpkin mixture into the prepared tin, alternating between the two. Swirl gently with a butter knife.
Bake the brownies for 35 minutes, or until a skewer or toothpick inserted into the center comes out clean.
Allow to cool completely in the baking tin before removing and slicing.