Preheat the oven Gas 6/200c/180c Fan Oven.
Line an 8 inch tin with non stick paper.
Mix the crushed biscuits and melted spread with a tablespoon of water until combined. Spread over the base of the tin and press down firmly. Put in the fridge to chill.
Mix the sugar, cornflour and lemon zest in a large bowl. Add the vanilla, soft cheese, creme fraiche, yogurt and eggs and beat until smooth and nicely combined.
Pour over the chilled biscuit base and bake for 40-50 minutes or until it has cracked slightly and has shrunk away from the sides of the tin. It should be golden on top and still slightly wobbly in the centre - it firms as it cools.
Leave to cool in the tin before removing. Transfer to a plate and chill in the fridge for at least an hour before serving.