| 250g digestive biscuits | 
crush to fine crumbs | 
Mix. Press onto base of greased 24cm springform cake tin. Chill 1 hour. | 
Scoop cheese onto base. Bake in moderately slow oven 1 to 1 1/2 hours without opening the oven door until golden brown on top. Turn off the heat and let the cake stand in the oven for two more hours. Open door, stand a further hour. | 
| 150g butter | 
melted | 
| 3 tablespoons sugar sugar | 
 | 
| 6 egg whites | 
  | 
Beat to stiff peaks  | 
| 225 caster sugar | 
  | 
Mix  | 
  | 
 Fold in | 
| 2 tablespoons cornflour | 
| 750g full fat soft cream cheese | 
  | 
 Beat in  | 
| 6 egg yolks | 
| 2 teaspoons vanilla extract | 
| 150ml double cream | 
  | 
 Slowly pour in, beating constantly  | 
| 150m sour cream | 
| teaspoon salt | 
 | 
  | 
 Add | 
| zest of 1 lemon | 
grated |