Wash the potatoes. Cook in boiling water for about 15 minutes. In the meantime, clean and wash the broccoli and divide into small florets. Cook in 200 ml boiling salted water for about 8 minutes. Then drain and store the vegetable water.
Grate cheese. Cut salmon ham into thin strips. Peel and finely chop the onion. Heat the fat in a pot. Fry diced onion until transparent. Add vegetable water and milk and boil up briefly.
Melt half of the grated cheese in it. Sprinkle with sauce thickener, bring to the boil again briefly. Season with salt, pepper, nutmeg and stock. Wash, chop and stir in the parsley. Heat broccoli and ham in the sauce.
Peel the potatoes and also add them to the sauce. Serve everything garnished with chervil. Sprinkle with the rest of the cheese.