prevent oven to 190C gas mark 4

cover base of dish with 1/2 of the potato slices

pour 1/4 of the beaten egg over the potatoes

sprinkle a little thyme, salt and pepper over the potatoes

cover with a layer of cheese

put the other 1/2 of the potatoes on top of the cheese

put another layer of grated cheese on top

pour the remaining egg and the milk over the final layer

add 3 knobs of butter and a sprinkle of breadcrumbs

put the lid on the dish and bake for 25 minutes

after 25 minutes, remove the lid and cook for another 5 minutes to crisp on top