Step 1: Prepare the Brownie Crust

1. Preheat your oven to 350°F (175°C). Grease a 9-inch springform pan and line the bottom with parchment paper for easy removal.
2. In a medium mixing bowl, whisk together the melted butter and sugar until smooth. Add the eggs and vanilla extract, whisking until fully combined.
3. Sift in the cocoa powder, flour, salt, and baking powder. Stir with a spatula until the batter is smooth and glossy.
4. Pour the brownie batter into the prepared springform pan, spreading it into an even layer. Bake for 15-18 minutes, or until the edges are set but the center is still slightly soft (it will finish baking with the cheesecake). Let the crust cool while you prepare the cheesecake filling.

Step 2: Make the Cheesecake Filling

1. Reduce the oven temperature to 325°F (163°C).
2. In a large mixing bowl, beat the cream cheese and sugar together with a hand mixer or stand mixer until smooth and creamy, about 2-3 minutes.
3. Add the eggs one at a time, mixing well after each addition. Scrape down the sides of the bowl as needed.
4. Mix in the vanilla extract and sour cream, beating just until combined. Be careful not to overmix, as this can introduce air bubbles that may cause the cheesecake to crack.
5. Pour the cheesecake batter over the cooled brownie crust, spreading it evenly with a spatula.

Step 3: Bake the Cheesecake

1. Place the springform pan on a baking sheet to catch any drips. Bake the cheesecake in the preheated oven for 50-60 minutes, or until the edges are set and the center is slightly jiggly.
2. Turn off the oven and crack the door open slightly. Let the cheesecake cool in the oven for 1 hour to prevent cracking.
3. Once cooled, remove the cheesecake from the oven and let it come to room temperature. Cover the pan with plastic wrap and refrigerate for at least 6-8 hours, or overnight, to fully set.

Step 4: Prepare the Caramel Topping

1. If using store-bought caramel sauce, warm it slightly in the microwave or on the stovetop until it’s pourable. If you prefer salted caramel, stir in 1/2 teaspoon of sea salt.
2. Spread the caramel sauce evenly over the chilled cheesecake, allowing some to drip down the sides for a dramatic effect.

Step 5: Garnish the Cheesecake

1. Sprinkle brownie chunks over the caramel layer, pressing them gently to adhere.
2. Drizzle melted chocolate over the top using a spoon or piping bag for a decorative finish.
3. For extra flair, add dollops of whipped cream around the edges of the cheesecake.

Step 6: Serve and Enjoy

1. Slice the cheesecake into 12 servings and serve chilled. Optional: drizzle each slice with extra caramel sauce or melted chocolate for an extra-indulgent touch.