1 For the base: Line an 8 x 8inch square tin with parchment paper, allowing the paper to come up the sides of the tin and leaving a few centimetres hanging over the edge. Preheat the oven to 175 degrees Celsius.
2 Put the biscuits into a food processor with the sugar and blend to a fine powder. Add the melted butter and blitz again, until well combined. You should have the texture of wet sand.
3 Press the biscuit powder into the base of the tin, packing tightly. Put the tin in the fridge to set while making the filling.
4 For the cheesecake filling: Put all of the cheesecake filling ingredients except the cream into a food processor and blend until smooth and fully combined. Alternatively, mix well in a bowl until smooth.
5 Fold in the whipped cream, and pour the mix into the tin, smoothing the top with the back of a spoon or a palette knife.
6 Put the square tin into a larger tin and place in the oven. Pour boiling water into the larger tin until the water comes halfway up the smaller tin. Close the oven and bake for 50-55 minutes. The cheesecake should have a slight wobble in the centre. Remove from the oven and leave to cool completely, overnight is preferable. You can also freeze it at this point.
7 For the lemon curd: Put all of the ingredients in a bowl over a pan of simmering water. Whisk continuously for about five to 10 minutes until the curd coats the back of a wooden spoon or until it has reached 75 degrees Celsius. Remove from the heat, cool slightly, pour into sterilised jars and seal. The lemon curd will keep for a few weeks in the fridge.
8 Slice the cheesecake into 12 bars, and drizzle with lemon curd to serve.