Heat the oven to 160C/140C fan/gas 3. Line the base and sides of a 20x30cm shallow cake tin with baking parchment.
Put the ginger biscuits into a food processor and whizz to very fine crumbs. Add the melted butter, using the pulse until well mixed. Tip the mixture into the tin and spread out evenly. Using the back of a metal spoon, press the mixture down firmly.
Clean the food processor bowl and add the ricotta, cream cheese, soured cream, eggs, caster sugar, cornflour, vanilla extract, lemon rind and juice. Whizz until smooth, then pour the mixture into the cake tin. Bake in the oven for about 40 mins until the mixture is lightly set all over. Remove and allow to cool to room temperature.
Whisk the cream to soft peaks. Spread thinly over the top of the cheesecake. Chill the cheesecake overnight.
To serve, remove the cheesecake from the tin and peel the paper from the sides. cut into 48 small squares or halve again to make 96 rectangles. Arrange on a serving plate. Put the lemon curd into a small disposable piping bag. Snip off the end and pipe zigzags on the cheesecakes. Alternatively, place a small raspberry on top of each square.