Step 1

Preheat the oven to 375 F/190 C/gas mark Line the bottom of your pan with parchment and lock the sides. Set aside.

Step 2

Prepare crust ingredients: Place the biscuits in a food processor and pulse until they have the texture of fine crumbs (or use ready-made graham crumbs). Alternatively, place the biscuits in a plastic bag and crush with a rolling pin.

Step 3

Combine crust ingredients: To a bowl add the crumb mixture, melted butter and 1 tablespoon of cocoa. Stir until thoroughly combined.

Step 4

Make cheesecake base: Cover the bottom of your pan with the crumb mixture pressing down firmly (you can smooth out the top using the bottom of a glass).

Step 5

Bake base: Bake in the centre of the oven for 15 minutes. Remove from the oven and set aside to cool. Increase the heat to 400 F/ 200 C/190 C fan/ gas mark In the meantime prepare the chocolate cheesecake filling.

Step 6

Melt chocolate: add pieces of chocolate to a glass bowl and place over a pot of gently simmering water, stirring occasionally. Remove the bowl from the pot when almost all the chocolate has melted (it will finish melting as you stir). Alternatively melt the chocolate in the microwave. Set aside while you prepare the rest of the ingredients.

Step 7

Beat cheese: Combine the ricotta with the cream cheese and beat (using the paddle attachment) on med-low speed gradually adding in the sugar until the mixture is smooth and creamy (1-2 minutes). Scrape the sides and bottom of the bowl often.

Step 8

Add cocoa: Add the cornflour, cocoa and vanilla extract and beat only until just combined.

Step 9

Add chocolate: Pour in the melted chocolate (make sure it’s cooled) and continue beating just to combine.

Step 10

Add eggs: Add the eggs one by one beating on low speed just until combined (do NOT overbeat the mixture at this point).

Step 11

Add sour cream: Add the sour cream just until combined (as above).

Step 12

Bake cheesecake: Brush the inside of the pan ring (ensure it's cooled completely) with a little melted butter and pour in the cheesecake filling. Tap gently against the counter to remove any air bubbles, smooth out the top and place in the centre of the preheated oven. Bake for 10 minutes then lower the temperature to 245-250 F/120 C/110 C fan. (If, like me, you are using a gas oven set the temperature to halfway between 'S' and 0 ensuring your oven doesn't switch off completely) Continue baking for 45 minutes then switch the oven off and leave the cheesecake inside for an hour (but do NOT open the oven door).

Step 13

Cool cheesecake: Open the oven door a little, wait for about 15 minutes then remove the cheesecake and leave to cool completely. It will still be a little wobbly but that's ok. Once cooled cover and refrigerate it (without removing the pan ring) for at least 6 hours before serving.

Step 14

Serve: Run a thin spatula around the cheesecake before carefully removing the pan ring. Decorate with chocolate shavings, fresh berries, whipped cream or fruit compote and enjoy!