Preheat the oven to 350°F (175°C). Line an 8-inch square pan with parchment, leaving overhang for easy lifting. Lightly grease the parchment.

Make the brownie base: In a microwave-safe bowl, melt the butter in short bursts until just liquid. Whisk in the sugar while the butter is warm.

Add the eggs and vanilla. Whisk for 30–45 seconds until the mixture looks glossy. This helps create a shiny, fudgy top.

Sift in the cocoa powder, flour, baking powder, and salt. Stir gently until no dry spots remain. Fold in chocolate chips if using. Reserve about 1/3 cup of the batter for swirling.

Spread the remaining brownie batter evenly in the prepared pan. It will be thick—use an offset spatula to smooth it out.

Make the pumpkin cream cheese swirl: In a medium bowl, beat the softened cream cheese and sugar until smooth. Mix in the egg yolk, pumpkin puree, pumpkin pie spice, vanilla, and a pinch of salt until creamy.

Spoon the pumpkin cream cheese mixture in large dollops over the brownie batter. Add small spoonfuls of the reserved brownie batter in between.

Swirl: Drag a butter knife or skewer through the batter in gentle figure-eights. Don’t over-mix—two or three passes are enough for a marbled look.

Bake for 28–34 minutes, until the edges are set and a toothpick inserted 2 inches from the edge comes out with moist crumbs. The center should have a slight wobble but not look wet.

Cool completely in the pan on a rack. For clean slices, chill for at least 1 hour before cutting into 16 squares.