Method

​1 Melt the butter and stir in the crushed biscuits. Press into the base of a 20cm (8-inch) loose-bottomed cake tin and chill.

2 Meanwhile, put the condensed milk and dark chocolate in a large glass bowl. Place the bowl over a pan of simmering water and stir until the chocolate has melted. Then take it off the pan of water and set aside for 5 minutes to cool slightly.

3 Using a hand whisk, mix the cream into the chocolate mixture and pour over the biscuit base. Once that is done, chill in the fridge for 12 hours or overnight.

4 For the optional decoration of chocolate curls: melt the dark or milk chocolate and spread this onto a marble or cold metal baking sheet. Chill until just set. Then, using a knife or a potato peeler, scrape across the chocolate to make curls. Scatter the chocolate curls over the tart and serve.