Sweeten the coffee with 1 Tbsp of sugar, then pour the espresso into a shallow bowl for dipping the ladyfinger cookies.
Prepare the Mascarpone
For traditional Italian method with raw egg yolks: In a bowl, stir the mascarpone with a fork to make it easier to work with. In a separate bowl, whisk 2of the egg yolks together with the sugar until frothy. Blend in a little of the whisked yolks into the mascarpone, then gently whisk in the rest. If too thick to spread, add the remaining egg yolk.For method with cooked egg yolks: Fill the bottom of a saucepan with about an inch of water and bring to a simmer. Meanwhile, in a heatproof bowl, whisk the 3egg yolks with sugar until airy and pale yellow. Then place the bowl over the saucepan of simmering water and whisk for about 6-8 minutes, or until the mixture resembles a thick custard, and reaches 140°F (60°C). Let cool at room temperature for about 20 minutes before incorporating the mascarpone cheese. Do not blend with the mascarpone while the egg mixture is still hot, as it will curdle.
Assemble & Chill
Briefly dip each cookie into the coffee, 2 to 3 seconds max (you want them to be moist, not soggy), and arrange in a dish to make one layer. Cut any cookies to fit before dipping, if needed.
Spoon a layer of mascarpone mixture on top.
Sprinkle with a thin layer of cocoa powder.
Repeat with 1 or 2 more layers.
Cover and refrigerate for 4 hours to overnight, to allow the tiramisu to thicken, the cookies to soften, and the flavors to meld to the fullest.
Serve
To serve, (if using a cake ring, press the tiramisu out onto a serving plate), grate chocolate on top, or use a peeler to make chocolate curls.
Ingredient Notes
Espresso coffee - You want a strong coffee flavor. If you can't make espresso, make regular coffee with very little water, or use granules.
Mascarpone - Get the good stuff to ensure it is thick and will thus set well. (Or you can easily make your own mascarpone.)
Liquor - To spike your tiramisu, add about 2 Tbsp of Kahlua, rum, cognac, or liquor of your choice to the coffee before dipping.
Lady Finger Alternative - You can use a sponge cake (such as a genoise cake, or tres leches cake) in place of lady fingers. Using a cake makes it easy to make a round tiramisu. To apply the coffee, you can drizzle it on or use a pastry brush.
Chocolate - If you find the chocolate is too brittle to make chocolate curls, it helps to warm up the surface of the chocolate by rubbing it (with clean hands), or by using a knife that you have heated with hot water.
In a 2-hour pinch
If you don't have a lot of time, you can freeze the tiramisu for 30 minutes before refrigerating, to speed up the chilling process. (Remember though: tiramisu is best the next day!)
Storing
With raw egg yolks, it is recommended to eat within the next day or two. If using cooked eggs, another few days. Or tiramisu can be frozen, then thawed in the refrigerator (not at room temperature) overnight.