Preheat the Oven: Preheat your oven to 350°F (175°C). Line a 9×13 inch baking pan with parchment paper, leaving an overhang on the sides for easy removal.

Prepare the Brownie Batter: In a medium saucepan, melt the butter and chopped chocolate over low heat, stirring until smooth. Remove from heat and let cool slightly. In a large bowl, whisk together both sugars, eggs, and vanilla. Stir in the melted chocolate mixture. Sift in the flour, salt, and cocoa powder. Fold gently until just combined. Pour the brownie batter into the prepared baking pan.

Prepare the Cheesecake Batter: In a separate bowl, beat the cream cheese until smooth. Add in the sugar, eggs, and vanilla extract, and continue beating until creamy. Pour the cheesecake batter over the brownie layer in the baking pan, spreading it evenly.

Add Raspberry Swirl: Warm the raspberry preserves slightly if needed to make it pourable. Drop spoonfuls over the cheesecake layer, then use a knife or skewer to swirl the jam into the batter, creating a marbled effect.

Bake: Bake in the preheated oven for 40-45 minutes, or until the center is set and a toothpick inserted into the middle comes out with only a few moist crumbs.

Cool: Allow the brownies to cool completely in the pan on a wire rack. Once cooled, lift them out of the pan using the parchment overhang and cut into squares.