Preheat oven to 350°F (175°C). Grease a 9x9 inch baking pan and set aside.
Melt the butter and chopped bittersweet chocolate together in a microwave-safe bowl, stirring until smooth. Let cool slightly.
In a large bowl, whisk eggs and sugar until light and fluffy. Gradually add the chocolate mixture and vanilla extract, mixing well.
Add the flour and salt, stirring gently until just combined. Do not overmix.
In a separate bowl, beat the cream cheese until smooth. Gently fold in the raspberries, taking care not to break them up too much.
Pour half of the brownie batter into the prepared pan. Spoon dollops of the cream cheese mixture over the batter, then top with the remaining brownie batter.
Using a knife or skewer, swirl the cream cheese mixture into the brownie batter to create a marbled effect.
Bake for 30 minutes or until a toothpick inserted near the center comes out with moist crumbs. Allow to cool completely before cutting into squares.
Notes
Store brownies in an airtight container at room temperature for up to 3 days or refrigerate for up to a week. They also freeze well.