Preheat your oven to 350°F (175°C) and line a 9x13 inch baking pan with parchment paper, leaving some overhang for easy removal.
In a medium saucepan, melt the butter and chopped dark chocolate together over low heat, stirring constantly until smooth. Remove from heat and allow to cool slightly.
Stir in 1 1/4 cups of granulated sugar and 1 teaspoon of vanilla extract into the chocolate mixture, mixing well.
Add the eggs, one at a time, beating well after each addition until fully incorporated.
Sift the flour and salt into the mixture, folding gently until just combined. Be careful not to overmix.
Pour half of the brownie batter into the prepared pan, smoothing it out evenly. Sprinkle the fresh raspberries on top.
In a separate bowl, beat together the softened cream cheese, 1/4 cup of sugar, 1 teaspoon of vanilla extract, and 1 egg until creamy and smooth.
Drop spoonfuls of the cheesecake mixture over the brownie batter and use a knife or skewer to swirl it into the batter. Top with the remaining brownie batter, smoothing it over the cheesecake layer.
Bake in the preheated oven for 30-35 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs but not wet batter.
Allow the brownies to cool in the pan for about 15 minutes before lifting them out with the parchment paper. Let them cool completely on a wire rack before cutting into squares.
Notes
Serve on a decorative plate, dusted with powdered sugar, and garnish with additional raspberries on top for a fresh touch.