step 1
Put the topping ingredients into a pan and heat gently until syrupy. Leave to cool.
step 2
Whizz the biscuits in a food processor to make fine crumbs. Mix with melted butter and then press into the base of the cake tin and smooth with a back of a spoon. Chill in the fridge.
step 3
For the filling, melt the chocolate over a pan of barely simmering water, then leave to cool slightly. In a mixing bowl, beat together the mascarpone, cream cheese, double cream until smooth. Whisk in the chocolate until thick.
step 4
Briefly fold half of the blackcurrant topping into the cream cheese mixture so it makes a ripple effect, but doesn't turn it purple. Spoon into the cake tin and chill in the fridge until set.
step 5
Transfer to cake stand and spoon over the remaining blackcurrant topping allowing the juice to drizzle over the whole cheesecake.