New York Style Baked Cheesecake

Ingredients

1.	Pre-heat oven to 190°C / 375°F / Gas Mark 5. Add the crushed biscuits and salt to the melted butter and stir until fully incorporated
2.	Tip the mixture into the bottom of a 20cm/8" spring form pan and press firmly with the bottom of a glass until it is level and compacted
3.	Bake in the oven for 20 minutes on a baking tray. Remove the base, and turn the heat up to Gas Mark 9 / 240°C / 475°F, leaving the tray in the oven
4.	Brush the base with a little of the egg white before it fully cools
5.	Add the cream cheese to a large bowl, and using a whisk, mix until smooth and no lumps remain
6.	Add in the sour cream, vanilla, sugar and lemon zest (if using)
7.	Beat the 4 eggs and yolk together, then add to the mixture a little at a time, stirring until just mixed
8.	Add the filling mixture to the base. Gently shake it to make any air bubbles rise, and run your finger around the edge of the filling to burst them.
9.	Place the tin on the warm baking tray and bake for 10 minutes, then turn the oven down to 110°C / 230°F/ Gas Mark ¼. Bake for a further hour or until set but with still a slight wobble in the centre
10.	Turn the oven off and leave the cheesecake to cool in the oven for at least 1 hour
11.	Serve chilled with some whipped cream or fruit