Brew the coffee, and while it's still hot / warm, dissolve the caster sugar. When the coffee has cooled to room temperature, stir in the Baileys. Transfer the coffee to a shallow bowl and set aside.
Cream
Chill a large mixing bowl and the beaters for 30 minutes until well-chilled. Get an extra-large bowl and fill it 1/3 full with ice water. Place the chilled mixing bowl in the water bowl and pour the cream in. Using an electric mixer, whip the cream on high speed with the chilled beaters until soft peaks form.
Keeping the cream chilled will help to prevent the cream from splitting and becoming butter and buttermilk. Once the cream splits, there's no way to reverse it, so be careful not to overwhip!
Chill the whipped cream in the fridge while you prepare the other components.
Mascarpone
To make super-fine sugar, place 2 tablespoons of caster / granulated sugar in the food processor and process until powdery.
Place the mascaropone and super-fine sugar in a medium mixing bowl and beat with an electric mixer until the sugar has been incorporated - don't overbeat as the cheese will become grainy. Stir in the Baileys. Set aside.
Egg Yolks
Fill a small pot with some water and bring to a boil. Turn the heat down to a simmer.
In a heat-proof mixing bowl (preferably glass or metal), combine the egg yolks, sugar and Baileys. Whisk it with a wire whisk slightly combined. Place the mixing bowl on the pot of simmering water - ensuring that the surface of the water is at least 1 inch away from the bottom of the bowl - pour away some hot water if necessary.
Whisk the mixture constantly until it thickens and a trail is left behind when the whisk is lifted from the mixture. This process takes about 5-10 minutes. (It'll take significantly longer if you doubled / tripled the recipe)
Once a trail is left behind when the whisk is lifted from the mixture, remove the bowl from heat and whisk it continuously until it has cooled to room temperature. (It must be cooled to room temperature before being incorporated with the other components.)
Fold the mascarpone mixture into the cooled egg yolk mixture, then fold the cream into the mix - fold as gently as possible as you want to retain as much air as you can to ensure a very light and airy concoction.
Assembly
Genoise: Using a brush, dab the genoise both sides generously with the Coffee Mix - the genoise is very soft and very absorbent!
Savoiardi: Dip one side of the Savoiardi into the Coffee Mix for 3 seconds, then turn and dip the other side for another 3 seconds (store-bought Savoiardi are not as absorbent as the genoise).
Place the genoise / savoiardi in the serving tin. Spread a generous layer of tiramisu-cream mix on top, followed by a layer of cocoa powder and/or grated chocolate. Repeat, ending with a layer of cocoa powder and grated chocolate.
Chill the cake/s in the refrigerator overnight for the flavours to mingle before serving.