Preparation Steps

• Preheat oven to 350°F (175°C). Grease and flour a 9-inch springform pan. Line the bottom with parchment paper.
• For the brownie base: In a medium bowl, whisk together melted butter and sugars. Beat in eggs one at a time, then stir in vanilla extract.
• In a separate small bowl, whisk together cocoa powder, flour, and salt. Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Stir in chocolate chips.
• Spread the brownie batter evenly into the prepared springform pan.
• For the cheesecake filling: In a large bowl, beat cream cheese and sugar until smooth. Beat in eggs one at a time, then mix in sour cream and vanilla extract until just combined. Do not overmix.
• Carefully pour the cheesecake filling over the brownie batter in the pan.
• Bake for 55-65 minutes, or until the edges are set and the center is slightly jiggly. Turn off the oven and let the cheesecake cool in the oven with the door ajar for 1 hour.
• Remove from oven and let cool completely on a wire rack. Refrigerate for at least 4 hours, or preferably overnight.
• For the hot fudge sauce: In a small saucepan, melt butter over medium heat. Stir in sugar and cocoa powder. Gradually whisk in evaporated milk.
• Bring to a boil, stirring constantly, then reduce heat and simmer for 2-3 minutes, or until thickened. Remove from heat and stir in vanilla extract.
• To serve, remove the sides of the springform pan. Spoon warm hot fudge sauce over the cheesecake.