Beat cheese thoroughly.
Gradually add sugar and cream well.
Add egg yolks—one at a time.
Stir in flour, sour cream and flavouring.
Fold in stiffly beaten egg whites.
Pour carefully into crumb-lined pan.
Bake at 300°F for 1 hour.
Turn oven off and leave cake in oven for 1 hour, with door slightly open.
This cheese cake is quite delicious plain, but may be topped with fruit or whipped cream.