Cream the ricotta and cream cheese,add the eggs,beating them in one at a time.Add the vanilla.Spoon in the flour and sour cream,mix well."It's going to be loose,don't worry",says Nanny.So don't worry.This works.Pour the mix into a 25 cm springform cake pan.Bake in a 325 deg oven for 1 hour,more or less,as in othe recipe...