NOTE: The water, vegetable oil and eggs for the cake are the ingredients required for the box of cake mix I used (betty crocker). Adjust ingredients for the box mix you have and use the liquid called for in the steps 2 and 3.
1. Preheat oven to 350 degrees and prepare a 9×13 inch cake pan.
2. Measure out water into a measuring cup, then remove 4 tbsp and put it in a small bowl.
3. Microwave the water in the small bowl until warm, then add 2 tbsp espresso powder. Stir until dissolved.
4. Combine ingredients, including espresso, according to box instructions and bake in 9×13 pan.
5. Once cake comes out of the oven, poke holes in the top of the cake. I used a knife sharpener.
6. Place 3 tbsp of kahlua into a small bowl and heat until warm. Add remaining 2 tbsp espresso powder and stir until dissolved.
7. Combine kahlua espresso mixture, remaining kahlua and sweetened condensed milk in a medium sized bowl, then pour evenly over the warm cake.
8. Refrigerate cake until cool.
9. While cake cools, make the topping. Combine egg yolks and sugar in the top of a double boiler, over boiling water. If you don’t have a double boiler, you can use a metal mixing bowl set over a pot.
10. Cook for about 8-10 minutes, with heat on low, stirring constantly.
11. When done, whip yolks with mixer until they thicken and yellow a bit.
12. Add mascarpone to whipped yolks and mix until smooth, scraping down the sides as needed.
13. If you have a second metal mixing bowl, use it for your whipped cream. If not, put mascarpone mixture into another bowl and get your metal mixer bowl clean.
14. Place metal bowl and whisk into freezer for about 15-20 minutes.
15. Remove bowl and whisk from freezer, add whipping cream to bowl and whip with mixer until stiff peaks form, about 5-7 minutes.
16. Fold whipped cream into mascarpone mixture.
17. Spread mixture evenly over the cooled cake and sprinkle cocoa over topping
18. Refrigerate until ready to serve.