I cook the whole mix, potatoes and cream etc in the microwave... the layers come a bit undone but you just pat it back down again and its all good

If all else fails just cook it longer in the oven... Its one of those dishes you can cook and let it stay in a warm oven for ages and it doesn't spoil

Nigella actually cooks her potatoes in the cream mix first in a big pot, but if you do it in a microwave you only have one dish to clean coz I cook it in the pyrex dish that can go in the oven too

*hugs*
Cailin