Preheat your oven to 350°F (175°C) and grease and flour three 8-inch round cake pans.

In a large mixing bowl, combine unsalted butter, granulated sugar, brown sugar, eggs, and sour cream. Blend until smooth and creamy for about 2-3 minutes.

In another bowl, sift together all-purpose flour, cocoa powder, baking powder, baking soda, and salt. Whisk until fully combined.

Combine the cocoa powder and instant coffee with boiling water in a small bowl, then fold into the cake batter.

Divide the batter evenly among the prepared cake pans and smooth the tops. Bake for 25-30 minutes until a toothpick comes out clean.

Allow the cakes to cool in the pans for about 10 minutes, then transfer to wire racks to cool completely.

Prepare your salted caramel sauce if not made in advance.

Whisk together cream cheese, cocoa powder, powdered sugar, and a pinch of salt until smooth, then incorporate the cooled salted caramel and heavy cream.

Trim the tops of each cooled cake layer and layer with frosting and salted caramel between each layer.

Let the cake sit at room temperature for about 30 minutes before serving.