Graham Cracker Cheesecake

Preheat the oven to 300 degrees F.

FOR THE CRUST:
Grind the graham crackers (sweet biscuits) in a food processor to fine crumbs. Place in a mixing bowl. Pour the melted butter over the crumbs, and stir to combine. Press into an 8-inch springform pan, lining the base and sides.

FOR THE CAKE:
Place the cream cheese, ricotta cheese and sugar in a food processor and process until smooth. (Alternatively you can use an electric mixer.) Add the eggs, 1 at a time, mixing well after each addition. Transfer to a bowl (if using a processor) and fold in the flour, sour cream, lemon juice and lemon zest. Pour into the crust-lined pan. Bake for 1 hour, or until the cheesecake is set in the middle. Turn off the heat and leave in the oven for another 15 minutes, with the door ajar. Remove from the oven and set aside to cool completely. Refrigerate for at least 2 hours before serving.