This cake is a version of a baked cheesecake. Use the best quality ricotta you can find. If your ricotta is quite wet it would pay to drain it through a muslin-lined sieve for a few hours. Cover and keep in the fridge if doing this. The biscuit base is very thin and gives a wonderful little bit of crunch.
Mix the butter, biscuits and hazelnuts together, then press into the base of cake tin. Cover and place a plate on top with some weights to press it down. Place in the fridge to firm up. (This can be done overnight).
Heat the oven to 180C.
Place the ricotta, mascarpone, sugar and egg yolks in a large bowl and beat together.
Whisk egg white until soft peaks form and fold through mixture with candied peel, vanilla, lemon zest and juice.
Spoon mixture into biscuit base and bake for 40 minutes. It should remain a little wobbly in the centre. Remove from oven and allow to cool.
To serve, fold lemon or passionfruit curd through whipped cream and spead a thin layer on top of lemon ricotta cake. Decorate with clementine slices, if using.
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Whisked egg whites should be of a similar consistency to the cheese mixture. Fold one tablespoon of egg white through first, then add remainder and fold through.