Combine egg yolks and sugar in the top of a double boiler (If you don’t have one, here’s an easy tutorial on how to make your own). Reduce heat to low, and cook for about 10 minutes, stirring constantly. Remove from heat and whip yolks until thick and lemon colored.
Add mascarpone to whipped yolks. Beat until combined. In a separate bowl, whip cream to stiff peaks. Gently fold into yolk mixture and set aside.
Line the bottom and sides of a large glass dish with the ladyfingers. Brush with coffee liqueur or strong coffee. Spoon half of the cream filling over the lady fingers. Repeat ladyfingers, coffee and filling layers. Garnish with sifted cocoa powder and/or shaved chocolate. Refrigerate several hours or overnight.
If desired, use a round biscuit cutter to cut individual portions of tiramisu from the dish. (This keeps calories down and also creates a nice presentation for guests!)