Preheat the oven to 350°F (175°C) and line a 9x13 inch baking pan with parchment paper, leaving some overhang for easy removal.
In a large mixing bowl, combine the melted butter and granulated sugar. Mix until smooth and creamy.
Add the vanilla extract and eggs to the butter mixture, one at a time, mixing until fully incorporated after each addition.
In a separate bowl, whisk together the flour, cocoa powder, baking powder, and salt. Gradually fold this dry mixture into the wet ingredients until just combined.
Stir in the semi-sweet chocolate chips until evenly distributed throughout the batter.
In another bowl, beat the softened cream cheese until smooth. Add the powdered sugar and orange zest, mixing until well combined.
Pour half of the brownie batter into the prepared baking pan and spread evenly. Then dollop the cream cheese mixture over this layer, using a spoon to create swirls like a marble effect.
Pour the remaining brownie batter on top, reserving some for decoration if desired. Use a toothpick or knife to create a marbled effect by swirling it through the top layer.
Bake in the preheated oven for 30-35 minutes or until a toothpick inserted in the center comes out mostly clean.
Allow the brownies to cool in the pan for at least 10 minutes before using the parchment paper to lift them out and cool completely on a wire rack.
Once cooled, cut into squares and sprinkle with Halloween-themed sprinkles for an extra festive touch.
Notes
Serve on a spooky-themed platter and add mini chocolate pumpkins or ghosts for decoration.