In a large bowl, beat together the cream and 1 tbsp of sugar until stiff (IMPORTANT: it must be stiff). Set aside.
In another large bowl, Beat together the egg yolks and 4 tbsp of sugar until nice and creamy.
Add the mascarpone, a spoonful at a time, to the egg mixture. Keep mixing it until smooth and creamy.
Add the cream into the mixture slowly, making sure it stays thick.
Time to assemble. In a flat bowl (wide enough to dip a biscuit in), add the coffee and liqueur.
In a medium-sized rectangle pyrex/serving dish, add a tbsp full of the cream. Spead it thinly on the bottom of the dish. This is just to make the biscuits stick.
Dip the biscuits (quickly, they must NOT soak up too much liquid. They need to still be firm. Layer the first layer of biscuits on the bottom, top with a layer of cream (not too much). We want to make 2 layers of biscuits.
I add some cocoa in the middle as well, but this is not necessary for this layer. Repeat the process so that you end with a layer of cream.
On the top, sift a thin layer of cocoa to end the process. You should just see cocoa on top. Cover the dish with cling wrap or foil (it must not touch the cocoa!). Pop into the fridge until ready to enjoy.