Gently melt the butter in a saucepan. Add the crushed biscuits and mix until the butter has been absorbed.
Remove from the heat and, while still warm, press the mixture (using the back of a spoon) into the bottom of a lined 23cm/9inch springform or flan tin. Leave to set for one hour in the fridge.
While it is chilling, grate the chocolate. Set aside in the fridge if your kitchen is warm.
In a bowl, whip the cream until it forms soft peaks.
In a separate bowl, beat the cream cheese until it is soft. Beat in the icing sugar and a shot of Baileys. Fold in the whipped cream and three-quarters of the chocolate. When the mixture is smooth, smooth it evenly onto the biscuit base.
Refridgerate and allow to set for at least two hours. If you can bear to leave it overnight, so much the better.
To serve, remove from the tin and decorate. You can either sprinkle the remaining grated chocolate over the top for a simple finish, or add some individual chocolates and flakes for a more elegant and ceremonial dressing.
Some people serve individual portions with additional cream, poured over or whipped into a peak.