Step 1

Grease and line the bottom of a 20cm (8 inch) springform tin. Crush the cookies into fine crumbs. The easiest way to do this is in a food processor, but you can also crush them by placing them in a sturdy plastic bag and bashing them with a rolling pin. Place the crumbs into a bowl, and add the melted butter. Stir together until the crumbs are evenly coated with the butter, and then spoon into the pre-prepared tin. Press the crumb mixture right up to the edges of the tin using the back of a spoon, and level out the top, pressing down to make sure it is nice and compact. Place the tin in the freezer to set whilst you make the topping.

Step 2

Break the orange chocolate up into pieces and place in a microwave-safe bowl. Melt in the microwave (stirring every 20 seconds) or over a pan of boiling water, until completely melted. Place in the fridge to cool slightly.

Step 3

To make the cheesecake topping, place the mascarpone cheese, cream cheese, sifted icing sugar, cocoa powder, and vanilla extract into a large bowl (or the bowl of your stand mixer fitted with the balloon whisk attachment). Beat until smooth. Add the slightly cooled melted chocolate to the bowl and mix well.

Step 4

In a medium bowl, whisk the double cream until stiff peaks are just about formed. Add the cream to the cheesecake mix, folding in gently to avoid knocking the air out of the whipped cream, until completely incorporated.

Step 5

Remove the cookie base tin from the freezer, and spoon the cheesecake batter on top of it. Spread out using the back of a spoon or a palette knife, getting it right to the edges of the tin. Smooth out the top and place in the fridge until set. This will take at least four hours, but overnight is preferable.

Step 6

Once set, carefully remove from the tin and place on a serving plate or board. If necessary, neaten up the edges with a palette knife. Drizzle with melted chocolate and top with chocolate orange slices and a sprinkling of orange zest (optional).