To make the chocolate ganache, melt the chocolate (dark or milk chocolate) in a water bath with the cream, without whipping it beforehand. Once both creams are ready, start putting the cake together in a suitable form with a ring (mine was 10" (26 cm) in diameter).
Assemble the cake in the following order - biscotti (dipped briefly in coffee), cream, chocolate ganache, cream again, biscotti, cream, chocolate ganache, cream, biscotti and cream.
Leave the cake in the fridge for a few hours or overnight, if you have the patience, then take it out, remove the ring, arrange biscotti (without dipping them in coffee beforehand) along the sides like a fence and sprinkle with crumbled biscotti on top.
You can tie it with a decorative ribbon for an even greater effect and to really impress the person you're making it for. That's what I did for my husband's birthday and he was left speechless. The cake is very light and lasted an entire week in the fridge without losing its taste qualities.