Preheat the oven to 180C/350F and grease and line and 8x8 inch square pan. I used grease proof paper and Wilton Bake Easy.

Tip the Oreo crumbs into a medium sized bowl and then pour melted butter over them. Stir until all the crumbs are coated in butter.

Tip the base into your prepared pan and press into a level layer, use your hands or a spatula. I used my hands.

Place into the oven for 10-12 minutes until slightly puffy and a the top feels a little bit crisp. Then remove and leave to one side for 5 minutes.

Make the cheesecake layer: Place cream cheese, eggs, sugar, vanilla, salt, orange extract and cocoa powder into a large bowl and beat until smooth, around 2 minutes with a hand mixer on med-high speed.

Pour in the melted chocolate and mix on low until well incorporated.

Tip cheesecake mixture on top of the biscuit base and smooth until level. Sprinkle the top with chunks of chocolate orange and place in the oven for 20-25 minutes until risen, the edges look matte and the centre only wobbles a little bit. If you stick a skewer into the centre it should come out clean, bar a few crumbs.

Leave to cool in the pan completely. Once cooled, transfer to a cutting board and slice into 9-12 bars.

To serve: Add a dollop of whipped cream, or pipe a swirl of it onto a cheesecake bar and then sprinkle with grated chocolate.

Chocolate Orange Cheesecake Bars will keep in an airtight container, in the fridge, for 3 days.