Hi there, I made Nigella's recipe for Cheesecake Ice Cream, which went fine, I cooked the custard, and churned it, then put in freezer and churned every hour for 3 hours but it's been in the freezer for 8 hours now and hasn't frozen. It is a thick saucy mixture still. I had it freezing in my churn bowl ice cream maker but just transferred it to a normal bowl now and stuck it back in freezer. Not sure if it couldn't freeze in the ice cream churn bowl, can you advise?
Nigella's Cream Cheese Ice Cream (from Forever Summer and on the Nigella website) is made with a custard comprising of milk, cream cheese, sugar and eggs. In this respect it is similar to any egg custard based ice cream and there is no particular reason why it will not freeze. Usually ice creams and sorbets don't freeze because they have too much sugar in them or contain a high amount of alcohol.
From the description of freezing we suspect that the ice cream just needs longer in the freezer. We also note that you mention churning the ice cream every hour for 3 hours. If you have an ice cream maker then this should not be necessary, usually you would churn the custard in an ice cream maker until it is very thick or almost solid (adding the cookie crumbs once the mixture has become thick), then transfer it to a container, put it in the freezer and leave until it is fully firm. All machines vary and you should always follow the manufacturer's instructions for your ice cream maker. Also make sure that the custard mixture is fully cooled (you can even chill it in the fridge) before folding in the lemon juuce and whipped cream.
If it is warm weather then you may also need to turn your freezer to a colder setting before making the ice cream (you can adjust the temperature back after the ice cream has frozen) as opening the door of the freezer frequently can cause the temperature in the freezer to rise slightly.
If you don't have an ice cream maker then you should freeze the mixture in a container until starting to freeze around the edges (usually about 1 hour) and then beat it, return it to the freezer and repeat this process another 2 times.