Boil the potatoes in a casserole.
Cut the potatoes in slices.
Peel and cut the onion in thin slices.
Cut the tartiflette cheese in tranches .
Preheat the oven at 200 degrees Celsius.
Cover the bottom of one oven form with thepotatoes.
Spread some smoked ham, blue cheese and onion slices on top. Sprinkle some shredded cheese.
Repeat last step until all the potatoes are used.
As the top layer spread the tartiflette slices over the rest.
Place in the oven for 30 minutes.
Take out and let rest 5 minutes before serving.