Step 1: Prepare the coffee mixture. In a shallow bowl, combine cooled espresso, coffee liqueur (if using), and 2 tablespoons sugar. Stir until sugar dissolves completely. Set aside.

Step 2: Make the zabaglione base. Fill a medium saucepan with 2 inches of water and bring to a simmer. In a large heatproof bowl that fits over the saucepan, whisk egg yolks and 3/4 cup sugar together. Place bowl over simmering water (don’t let bottom touch water) and whisk constantly for 5-7 minutes until mixture is thick, pale, and reaches 160°F.

Step 3: Cool the egg mixture. Remove bowl from heat and continue whisking for 1 minute to cool slightly. The mixture should be thick enough to coat the back of a spoon.

Step 4: Add mascarpone. Once egg mixture has cooled for about 5 minutes, gently fold in room temperature mascarpone cheese using a rubber spatula. Mix until completely smooth with no lumps.

Step 5: Whip the cream. In a separate bowl, whip cold heavy cream to stiff peaks using an electric mixer. This takes about 2-3 minutes on high speed.

Step 6: Combine cream and mascarpone mixture. Gently fold whipped cream into mascarpone mixture in three additions, being careful not to deflate the cream. The final mixture should be light and fluffy.

Step 7: Begin assembly. Quickly dip each ladyfinger into coffee mixture for 1 second per side they should be moist but not soggy. Arrange dipped ladyfingers in a single layer in a 9×13 inch dish.

Step 8: Add first cream layer. Spread half of the mascarpone mixture evenly over the ladyfingers using an offset spatula. Make sure to reach all corners and edges.

Step 9: Repeat layers. Dip remaining ladyfingers in coffee and arrange over cream layer. Top with remaining mascarpone mixture, spreading evenly for a smooth finish.

Step 10: Chill the tiramisu. Cover tightly with plastic wrap and refrigerate for at least 4 hours, preferably overnight. This allows flavors to meld and the dessert to set properly.