Preheat oven to 180°C and grease a 23cm springform tin.
Crush biscuits into fine crumbs using a plastic bag and rolling pin.
Mix melted butter with crumbs and press firmly into the tin base.
Bake the base for 10 minutes until golden and let cool.
Reduce the oven temperature to 160°C.
Beat cream cheese and sugar until smooth, then mix in sour cream and flour.
Gradually beat in the eggs and vanilla without incorporating too much air.
Pour filling over the base and bake for 45 minutes until slightly wobbly.
Turn off the oven and let the cake cool inside with the door ajar.
Remove from the oven to cool completely before taking it out of the tin.