Put the biscuits in a polythene bag and crush with a rolling pin or process in a food processor until crushed. Mix with the ginger and melted butter.
Divide the biscuit mixture between 6 double-thickness paper muffin cases and press down firmly with the back of a teaspoon. Place in the sections of a muffin tray.
Beat the cream cheese in a bowl with the sugar and egg. Put the chocolate with the brandy or liqueur and water in a heatproof bowl, set over a saucepan of very gently simmering water and leave until melted, stirring frequently until smooth. Stir into the cream cheese mixture and divide between the paper cases.
Bake in a preheated oven, 160°C (325°F), Gas Mark 3, for 20 minutes or until the surface feels lightly set – the cheesecakes will set further as they cool. Leave in the tin to cool completely.
Whip the cream in a bowl until just holding its shape. Remove the cheesecakes from the paper cases and top with a spoonful of cream. Decorate with chocolate curls or shards.