Melt the butter over a low heat. Crush the biscuits to a coarse crumble and then combine with the butter.
Lay stainless steel serving rings on a lined baking tray and then add the biscuit mixture to the rings. Press down firmly to make the base. Chill in the fridge while you prepare the cheesecake mixture.
Place the gelatine leaves in a bowl of cold water to soften.
Zest the lemons, set aside.
Juice the two lemons, and warm gently over a low heat. Strain the softened gelatine leaves, and squeeze out any excess water. Add the gelatine to the warm lemon juice and stir until dissolved.
Use a spatula to work and soften the cream cheese. Fold in the yoghurt, then mix in the sugar, lemon zest and juice.
Spoon the mixture on top of the biscuit bases, smoothing the surface with the back of a wet spoon.
Transfer the cheesecakes to the fridge and chill for at least 2 hours to ensure that the cheesecakes are set.
Stir the raspberries with the icing sugar, and lightly bruise them to extract some juice. Set aside until needed.
To serve, spoon the raspberry topping over each cheesecake.
Place the rings on individual plates, and using either a blow torch or very warm hands, heat the metal ring until you can loosen the cheesecake.
«You can use frozen raspberries when fresh ones are out of season, in which case, gently heat them through with the sugar to obtain a compote. Chill completely before using.»