First, make the crust. Use a food processor or blender to blitz the Oreos into fine crumbs (you could also add them to a ziploc bag and bash them with a rolling pin!). Add the melted butter and blitz again till the mixture clumps together when pressed between two fingers.
Line a 9x5 loaf pan with non stick baking paper, leaving a little overhang for easy removal. Tip the buttery crumbs into it. Press down with a spatula or your fingers, firmly and evenly packing the crumbs down over the base and into the corners of the pan. Chill in the fridge for 20 mins.
Meanwhile, preheat the oven to 160 C.
Chop the chocolate into small pieces and place in a microwave-safe bowl. Heat in 10 second increments until melted, stirring to smoothen out any lumps. Set aside to cool slightly.
Wipe the bowl of the food processor out and make the filling. (If you made the Oreo crumbs by hand and don't have a food processor, just use a mixing bowl and hand mixer for this step which is what I did).
For the filling, beat the cream cheese for a few seconds to soften and smoothen it, then add the yoghurt, cocoa, eggs, vanilla and sugar. Beat to combine, but do not over mix the batter. Now pour in the melted chocolate and beat one final time until combined.
Pour the filling out onto the chilled Oreo base and bake for 30 to 35 minutes until the center still has a wobble and the edges are puffed. Allow to cool in the oven for 20 minutes, then let the cheesecake cool completely at room temperature. Place it in the fridge to chill overnight.
Use the paper overhang to lift the cheesecake out of the pan (run a sharp knife around the edges if needed to loosen it), then slice into 6 triangular pieces, or smaller squares if you prefer. Dig in!
Cheesecake should be stored in the fridge at all times, where it will keep for a week. It will keep for about 2 months in the freezer. Happy baking!