Preheat your oven to 350°F (175°C). In a large mixing bowl, whisk together the buttermilk, sour cream, vegetable oil, granulated sugar, brown sugar, and eggs until smooth and combined.

In another bowl, sift together the all-purpose flour, cocoa powder, baking soda, baking powder, and salt. Gradually mix the dry ingredients into the wet mixture until just combined.

In a small bowl, dissolve the cocoa powder and instant coffee in 1 cup of boiling water, stirring until fully combined. Fold this warm mixture into your cake batter until uniform.

Divide the batter evenly among three greased 8-inch round cake pans. Bake for 25 to 30 minutes. Check for doneness with a toothpick.

While the cakes cool, prepare your salted caramel sauce by combining sugar and water over medium heat until it reaches a rich amber color. Add heavy cream and a pinch of salt, then cool.

In a mixing bowl, beat the cream cheese until creamy. Gradually add in cocoa powder, powdered sugar, and salt. Then add cooled salted caramel sauce and melted dark chocolate.

Once cakes have cooled, level them and place the first layer on a plate, adding frosting and drizzling salted caramel. Repeat with the second layer, and frost the top and sides.

Let your cake sit at room temperature for at least 30 minutes before slicing to allow flavors to meld.