Make the coffee syrup: In a shallow bowl wide enough to dip the ladyfingers in, combine the coffee and 2 tablespoons Kahlua. Stir and set them aside.
Make the cream mixture: In a small saucepan or pot over low heat, simmer about an inch of water and place a heatproof bowl over it. Make sure the water does not touch the bottom of the bowl, or it will cook the eggs. Make the zabaglione by combining the egg yolks, ¼ cup granulated sugar, and ¼ cup Kahlúa. Constantly whisk the egg mixture for 12-15 minutes. It's ready when the mixture has thickened, doubled in volume, and is lighter in color. It should leave thick trails as you drag the whisk. Immediately take the bowl out of the heat and set it aside to cool.TIP: Cool the zabaglione in the fridge for about 5 minutes or at room temperature for about 15 minutes. A warm mixture will deflate the whipped mascarpone mixture or cause it to curdle.Combine the mascarpone cheese, heavy cream, powdered sugar (or 2 tablespoons granulated sugar), and vanilla extract in a large bowl. With a hand mixer (or a stand mixer) starting on low speed and increasing as you go along, whip until smooth and incorporated. It will only take a little over a minute.Using a spatula, fold in about a cup of the mascarpone cream mixture into the cooled zabaglione. You do this because mixing them together all at once may deflate the whipped and airy mascarpone mixture. Combine the rest of the mascarpone mixture and the zabaglione. Mix them together until well blended.
Assemble: Quickly dip the ladyfingers in the coffee syrup one at a time. Arrange them in a 9×13-inch baking dish.Spread half of the cream mixture evenly on top and dust with cocoa powder.Repeat the same layers: lay the coffee-soaked ladyfingers on top and spread the remaining cream mixture. TIP: Avoid oversoaking the ladyfingers, so they don't get soggy. If you are using the soft and cake-like variety (as opposed to dry and crunchy), brush the coffee on them instead of dipping.
Chill: Cover with plastic wrap and chill for at least 4 hours, preferably overnight, until set and the ladyfingers have softened.
Serve: As an option, make some chocolate shavings. Using a sharp knife, slice the chocolate as thinly as you can on a cutting board, almost like scraping the edges of the chocolate bar. Use parchment paper to catch all the little pieces. Dust with cocoa powder and sprinkle some chocolate shavings on top right before serving.
Store: Keep the tiramisu in an airtight container ideally for about 3 days in the fridge or in the freezer to extend its shelf life. Let it defrost in the refrigerator or at room temperature for about 30 minutes before serving — dust with cocoa powder and top with chocolate shavings.
Ladyfingers or Savoiardi: These sponge cake biscuits have a crisp and dry texture, perfect for dunking in syrup without getting soggy. There is a soft and cake-like variety that you can also use, but instead of dipping, a light brushing of the coffee syrup is enough.
Strong coffee: Espresso or instant espresso is preferred, but you can also use brewed coffee or instant coffee (just make it strong).
Kahlúa: You may also use Tia Maria, sweet or dry Marsala wine, brandy, dark rum, Bailey's, Frangelico, or dessert wines like Madeira or Port. While tiramisu typically contains alcohol and is delicious that way, you can omit and use more coffee instead or add vanilla extract for more flavor.
Mascarpone cheese: This Italian version of cream cheese is rich with more fat content but softer and less tangy than American cream cheese, which you can also use in a pinch. Heavy cream: While other recipes call for whipped egg whites, I used heavy cream to lighten the mascarpone mixture.
Chocolate bar: You can use your favorite chocolate bar or baking chocolate (bittersweet or semi-sweet) that you like eating out of hand — an optional ingredient but highly recommended.