Step 1: Preheat your oven to 350°F (175°C). Grease and flour a 9x13 inch baking pan.
Step 2: In a large bowl, prepare the chocolate cake mix according to package directions, but also stir in the 1 cup of sour cream until just combined. Pour the batter evenly into the prepared baking pan.
Step 3: In a separate medium bowl, beat the softened cream cheese, softened butter, powdered sugar, and vanilla extract with an electric mixer until smooth and creamy.
Step 4: Drop spoonfuls of the cream cheese mixture over the chocolate cake batter in the pan. Sprinkle the 1/2 cup semi-sweet chocolate chips and chopped pecans or walnuts (if using) evenly over the top.
Step 5: Using a knife or a skewer, gently swirl the cream cheese mixture into the chocolate batter to create a marbled effect, taking care not to overmix.
Step 6: Bake for 30-35 minutes, or until a toothpick inserted into the center of the cake comes out clean. The top will be cracked, which is exactly what you want!
Step 7: Remove the cake from the oven. While still warm, gently poke holes all over the top of the cake using the handle of a wooden spoon or a skewer.
Step 8: Slowly pour the entire jar of caramel topping over the warm cake, allowing it to seep into the holes. You can warm the caramel slightly to make it easier to pour.
Step 9: Let the cake cool completely on a wire rack before serving. This allows the caramel and cream cheese to set. Once cooled, slice and enjoy!