01 - Preheat oven to 350°F. Line a 9-inch square baking pan with parchment paper, allowing overhang on sides for easy removal.
02 - Melt butter in microwave-safe bowl. Whisk in sugar, eggs, and vanilla until mixture becomes glossy. Sift in flour, cocoa powder, and salt. Fold until just combined. Spread batter evenly into prepared pan.
03 - Beat cream cheese and sugar with electric mixer until completely smooth. Add eggs one at a time, mixing well after each addition. Blend in vanilla and sour cream until incorporated.
04 - Pour cheesecake mixture evenly over brownie layer. Bake for 45-50 minutes until center is just set and edges are lightly golden. Cool completely at room temperature.
05 - Refrigerate for at least 2 hours until completely firm before adding topping.
06 - Combine unwrapped caramels and heavy cream in saucepan or microwave-safe bowl. Heat, stirring constantly, until melted and smooth.
07 - Pour caramel mixture over chilled cheesecake. Spread gently to cover surface. Chill 30 additional minutes until caramel sets. Slice into bars and serve.