I cooked sum a while ago and it was okay but a bit grainy. I think this is because I didn't beat it long enough after taking it off the heat but that's because it was already setting and hard-ish, is that because it was too hot?
Also I've had a look at nigella's recipe and she's very ambiguous it looks as though she takes it straight off the heat and beats it without resting it for five minutes in between as all the other recipes seem to say, am I misunderstanding that?