Grease a round loose bottom 15cm/6" cake tin and place a piece of greaseproof paper around the bottom. Crush the biscuits by placing them all in a bag and bashing them up to a breadcrumb consistency using a rolling pin or use a food processor. Gently melt the butter in a small saucepan over a low heat and stir in the crushed biscuits, ensuring they absorb all the melted butter. Spoon the biscuit crumbs into the cake tin. Use a metal spoon and your fingers to press the biscuit crumbs down firmly and evenly. Chill in the refrigerator for about 1 hour until set.
Coffee flavouring :-
Combine the hot water with the coffee and granulated sugar in a small bowl. Stirring to remove any lumps, then allow to cool. Do this as soon as you’ve put the cheesecake base in the fridge.
Cheesecake filling :-
Place the cream cheese, icing sugar and vanilla extract in a stand mixer bowl then whisk until smooth. Pour in the double cream and continue beating until the mixture is completely combined. Then fold in the cooled coffee mixture. Spoon the cream cheese mixture over the biscuit base. Make sure that there are no air bubbles by smoothing the top of the cheesecake with a palette knife or metal spoon. Place the cheesecake into the fridge to chill for 4 to 6 hours. If you can make this the day before and chill overnight, then even better.
Before serving, remove from fridge for 10 minutes or so to allow the cheesecake to return to room temperature. To remove it from the tin, place the base on top of a can, and gradually pull the sides of the tin down. Slip the cake onto a serving plate, removing the lining paper and base. Decorate with the walnut halves.
*Folks in the U.S. use Graham Crackers if you can’t get digestive biscuits.