Grease a tart mould (24 cm Ø; with lifting base) and dust with flour. Preheat the oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer). For the base, peel, wash and coarsely grate the potatoes.
Mix well with flour and 1 egg. Season with 1 teaspoon salt, pepper and a pinch of nutmeg. Press the mixture into the mould to form a base, forming a rim. Bake in a hot oven on the lowest shelf for about 15 minutes (see
In the meantime peel and finely dice the onion. Clean the mushrooms and possibly wash and quarter them. Wash, clean and roughly grate the zucchini. Heat the oil in a large pan. Sauté the mushrooms in it while turning them.
Add the onion and zucchini and fry briefly. Season with salt and pepper. Stir in ham.
Finely grate the cheese. For the glaze, whisk cream and 3 eggs. Season with salt, pepper and nutmeg. Remove the Rösti base from the oven and spread the vegetable and ham mix on top. Pour the icing evenly over it. Sprinkle with cheese.
Continue baking for approx. 30 minutes at the same temperature, also on the lowest shelf.
Remove the hash browns from the oven and let them rest for about 10 minutes. Carefully lift out of the mould. Sprinkle with marjoram leaves as desired.