Remove the eggs and mascarpone cheese from the refrigerator and bring them up to room temperature. Preheat the oven to 350F. Line a large jelly-roll pan with parchment paper and spray the sides with a little bit of non-stick cooking spray.

Prepare the sponge cake first: place the eggs and sugar into a mixer bowl and whisk on high speed for 8 to 10 minutes until thick, pale and almost white in color. Meanwhile, combine the flour and baking powder. Sift the flour in small portions into the whisked eggs, folding in by hand with a spatula. Mix gently but thoroughly after each addition, keeping the eggs fluffy. Pour the cake batter into the prepared pan and spread it to edges evenly.

Bake the sponge cake in the preheated oven for 15 to 17 minutes, just until top of the cake turns a golden color. Remove it from the oven and immediately run a knife along the edges of pan to release cake from sides. Sprinkle the top of the cake with a light dusting of confectioner's sugar. Spread a large, clean kitchen towel over the sponge cake. Invert the cake and remove the parchment paper (leaving the parchment paper on will sweat the cake). Carefully roll the cake into a log, using the kitchen towel as a wrapper. Set the cake onto cooling rack to cool completely.

Next, prepare the tiramisu filling: prepare a double boiler. Fill a small pot halfway with water and bring it to a simmer over medium heat. Meanwhile, whisk together the egg yolks and sugar in a medium-sized stainless steel/glass bowl. Make sure the bowl fits over the saucepan but does not touch the water! Place the bowl with the egg yolks over the simmering water and whisk constantly for 10 minutes. The egg yolks need to be cooked very slowly. The mixture will become thicker and more pale in color and the sugar will start to dissolve. Check the water often to make sure it's not boiling, but just simmering so egg yolks don't cook too quickly.

Remove the egg yolks from the heat and pour the mixture into a mixer bowl. Whisk on high speed for 3 to 4 minutes, until the mixture is thickened. Add the softened mascarpone cheese and vanilla and whisk again for a few minutes until no clumps remain. Cover the bowl and set it into refrigerator to cool for about 20-30 minutes.

Pour the chilled heavy cream into a larger mixer bowl and whisk it on high speed for 3 to 4 minutes, until stiff peaks form. Gradually fold in chilled egg and mascarpone mixture, mixing gently until well combined, about 1 minute. Don't overmix the filling; overmixing can cause the filling to separate. Cover the bowl and set into refrigerator to cool for 10-15 minutes.

Once the cake has cooled, gently unroll cake roll. Combine the coffee and liqueur in a small bowl. Frangelico is a sweet hazelnut liqueur but can be replaced with other liquors such as Kahlua, rum, or cognac. Use a spoon to pour coffee over entire sponge cake evenly, soaking the cake generously.

Reserve a third of the prepared filling for garnishing the top and keep it refrigerated. Spread the remaining two-thirds of the filling evenly across sponge cake, leaving about 1-inch margins around the edges. Gently roll up the cake roll the same way it was rolled initially. Place it onto serving tray. Spread a thin crumb coat of frosting on the outside and sides of cake.

Place the reserved filling into a pastry bag, tipped with a round tip. Garnish the outside of the cake (watch video tutorial for instructions) by adding dollops of cream, then gently spread each dollop with the back of a spoon. Alternatively, simply spread the frosting evenly around the cake roll.

Place the cake into refrigerator and let set for a few hours or overnight, preferably. Dust the top with cocoa powder right before serving.