Prepare the base: Crush the biscuits and combine with the melted spread. Press the mixture into the bottom of the springform cake tin and chill for 30 minutes.
Make the filling: Dissolve the jelly crystals in 250ml boiling water, then add the gelatine and stir until dissolved. Let cool completely.
Combine ingredients: In a food processor, combine the cooled jelly, yogurt, vanilla, quark, and sweetener. Blend until smooth.
Assemble: Pour the filling over the chilled base and cover. Refrigerate overnight, or until set.
Serve: Loosen the edges of the cheesecake and transfer to a serving plate. Dust with cocoa powder and cut into wedges.
Optional Variation: For a richer flavor, you can add a layer of crushed Oreos or digestive biscuits to the base.
