Line the base of a 20cm springform cake tin with baking parchment. Melt the butter in the microwave in 30-second bursts. Meanwhile, blitz 300g of the Oreos in a food processor until you have coarse crumbs. Transfer to a bowl, then stir through the melted butter until it has a texture like damp sand.

Tip the mixture into the lined tin, using the back of a spoon to smooth and flatten. Keep chilled while you make the filling.

Lightly crush most of the remaining Oreo biscuits, reserving some to decorate. Put the double cream, soft cheese and icing sugar in a large bowl. Beat using an electric whisk to stiff peaks, then fold in the crushed Oreos. Spoon onto the chilled base, flatten the top with a spoon and chill for 5-6 hrs until firm.

Melt the chocolate in short bursts in the microwave or in a heatproof bowl set over a bowl of simmering water (ensuring the bowl doesn't touch the water). Leave to cool slightly, then remove the chilled cheesecake from the tin and drizzle over the chocolate. Decorate with the remaining Oreos.