1 ¾ cups graham cracker or digestive biscuit crumbs
½ cup melted butter
5 8-ounce packages cream or 6 200-gram packages cream cheese
1 ¾ cups sugar
3 tablespoons flour
1 ½ tablespoons lemon zest (optional)
½ teaspoon vanilla
2 egg yolks
¼ cup whipping cream (not whipped)
Preheat oven to 500 degrees F (260 degrees C)
Wrap the outside bottom of a 9 inch (23cm) springform pan in foil. Combine crumbs, melted butter, and sugar and press on the sides and bottom of the pan.
Blend together cream cheese, sugar, flour, lemon zest and vanilla and mix until smooth. Add eggs and yolks one at a time mixing well after each addition. Blend in whipping cream. Turn cream cheese mixture into springform pan and bake 10 minutes. Reduce heat to 200 degrees F (100 degrees C) and bake 1 hour. Cool in a draft-free place and then refrigerate four hours before serving.