Preheat your oven to 350°F (175°C) and grease a 9-inch springform pan. In a bowl, combine melted butter, granulated sugar, brown sugar, eggs, and vanilla until smooth.

In another bowl, whisk flour, cocoa powder, and salt. Blend dry ingredients with wet mixture until just combined. Pour brownie batter into the prepared pan and bake for 20-25 minutes or until a toothpick comes out slightly fudgy.

While the brownie base cools, prepare the cheesecake filling. In a large bowl, beat softened cream cheese until creamy. Gradually add granulated sugar, sour cream, and vanilla, mixing well. Add eggs one at a time, blending gently.

Once the brownie base has cooled, pour the cheesecake filling over it, spreading evenly. Bake in a preheated oven at 325°F (160°C) for 40-50 minutes until edges set and center is slightly jiggly.

To make caramel sauce, place sugar and splash of water in a saucepan over medium heat. Stir until sugar dissolves and turns amber, about 8-10 minutes. Remove from heat, whisk in butter and heavy cream, and add salt if desired. Let sauce cool slightly.

After cooling cheesecake, refrigerate for at least 4 hours or overnight for firmer texture. Just before serving, drizzle with caramel sauce and slice into portions.