Preheat the oven to 350º Fahrenheit. Grease a 9x13 baking pan with cooking spray.
Make the cake:
In a large bowl, beat together the cake mix, milk, eggs and oil. Beat well, scraping the sides of the bowl as needed. We like to use a hand mixer or stand mixer to make sure it is blended well.
Pour the batter into the prepared pan. Bake for about 30 minutes, or until the center bounces back when you touch it.
Allow the cake to cool to room temperature.
Make the coffee drizzle:
In a medium bowl, whisk together the condensed milk, Kahlua, cocoa powder, espresso powder and salt. Mix well.
Use the pointed end of a wooden spoon (or a large fork) and poke holes all over the cake.
Pour the coffee drizzle evenly over the entire cake. Pour slowly so it has time to sink into the holes. Loosely cover and refrigerate the cake for 2 hours.
Make the frosting:
Beat together the sugar, mascarpone cheese and Kahlua. Mix well.
Add the heavy whipping cream. Use a stand mixer or high powered hand mixer to beat the mixture until stiff peaks form.
Spread the frosting on the cooled cake.
Dust with cocoa powder.
Cover and refrigerate until serving.
The calories shown are based on the cake being cut into 15 pieces, with 1 serving being 1 slice of cake. Since different brands of ingredients have different nutritional information, the calories shown are just an estimate. **We are not dietitians and recommend you seek a nutritionist for exact nutritional information.**