Boil potatoes with their skins in salted water for 20 minutes, peel them and leave to cool. Peel and dice the onions, fry them with marjoram in hot oil until translucent. Add the mince, fry, salt, pepper. Pour in the pils, let it simmer. Dice ham, rinse parsley, chop. Mix both with the hack.
Heat the butter in another saucepan, sprinkle with flour and sweat. Pour in the cream and milk while stirring and simmer for 5 minutes. Salt, pepper and let cool down a little. Stir in the egg yolks.
Preheat the oven to 200 degrees.
Clean the leek, rinse and cut into 1/2 cm thick slices. Blanch in boiling salted water for 1 minute and rinse in cold water. Cut the potatoes into 1.5 cm cubes. Mix both with the mince, salt and pepper.
Pour the mixture into a buttered baking dish. Pour the bechamel sauce over them and sprinkle with cheese. Cook in the oven on the middle rack at 200 degrees for 30 minutes.