Pass through a sieve and season. When you try the milk you should feel that the level of salt is slightly higher than you like because potatoes take lots of salt before you can feel it.
Put a bit of milk at the base of the mould so the first layer of potatoes doesn't stick.
On top of that lay 2 layers of potato slices.
On top of that add more of the milk until you can see it peeking through the potatoes. Then add salt, pepper and a bit of grated cheese.
Flatten out the potatoes using a spatula, cover with cling film and take to a preheated oven at 180C for 40min-1hour or until the potatoes are well cooked. You know they're done when you can easily put a knife through the layers.
Halfway through the cooking process remove the tin foil and check if it has dried too much; you should be able to see milk and cream peaking though the potatoes. If it needs more liquid, fill with the excess you had left. Also flatten the potatoes once again, put the foil back on and into the oven to finish cooking.
Remove the tin foil and add the rest of the cheese.
Return to the oven until it's golden on top, about 15-20min.