Method

Blitz the biscuits in a food processor until you've got even, small crumbs. Alternatively, put the biscuits in a clean food bag and crush by hitting with a rolling pin.

Mix the biscuits with the butter and cocoa. Pour into a springform cake tin. Spread out evenly, then use the base of a glass to press down firmly. Refrigerate while you continue.

Using an electric whisk, mix the cream cheese, cream, sugar and vanilla extract until you've got stiff peaks. Stir through the peanut butter until well mixed.

Spon on top of the biscuit base, and use a spatula to smooth out the top.

Melt the chocolate. You can do this in the microwave or over a simmering water.

Dollop the chocolate on top of the cheesecake, then use the tip of a knife to marble the chocolate. 

Set for at least 6 hours before serving (leave overnight if possible). Dig in!