Preparation Steps

• Preheat the oven to 325°F. Grease a 9-inch springform pan and line the bottom with parchment paper.
• Melt the butter and bittersweet chocolate together in a heatproof bowl over simmering water. Stir until smooth and set aside.
  1 cup unsalted butter
• In a large bowl, whisk together the sugar and eggs until well combined. Slowly add the melted chocolate mixture and mix well.
  1 cup unsalted butter
• Add the flour and stir just until incorporated. Pour the batter into the prepared pan and set aside.
  1 cup unsalted butter
• In a separate bowl, beat the cream cheese, sour cream, powdered sugar, and vanilla extract until smooth and creamy.
  1 cup unsalted butter
• Pour the cream cheese mixture on top of the brownie batter and gently swirl with a knife to create a marbled effect.
• Bake for 35 minutes until the center is set but still slightly jiggly. Let cool completely before removing from the pan and serving.