Preheat your oven to 325°F (163°C). Line a 9x9-inch baking pan with parchment paper.

Melt bittersweet chocolate with unsalted butter in a medium saucepan over low heat, stirring until smooth.

In a large mixing bowl, whisk together eggs, granulated sugar, pure vanilla extract, and salt until pale and thickened.

Gently stir in the melted chocolate, then fold in all-purpose flour until just mixed, reserving ⅓ cup of batter.

In a separate bowl, beat softened cream cheese until creamy. Gradually add granulated sugar, then mix in one egg and vanilla extract.

Pour brownie batter into prepared pan, then dollop cheesecake batter over it without disturbing the brownie base.

Dollop reserved brownie batter on top, creating a marbled effect.

Mash raspberries with sugar and corn starch; swirl over layers.

Bake for 30-35 minutes until edges are golden and center is set.

Cool completely on a wire rack and refrigerate for at least 1 hour before slicing.