Crush the biscuits by placing them into a bag or clean tea towel and hitting with a rolling pin. Pour the crumbs into a bowl and mix with the softened butter. Place two 5cm/2in chefs' rings onto serving plates and fill with the crumb mixture to form the base of the cheesecake.
Place the cream cheese into a bowl with the chopped stem ginger and about four tablespoons of the syrup from the jar and mix well. Spoon the mixture into the rings and smooth the top with a palette knife.
Sprinkle each cheesecake with the grated chocolate, then top with the ginger pieces.
To loosen the rings, quickly warm around the edges using a warm cloth or a mini-blowtorch, then lift off the rings.