Wash the potatoes and boil in water for about 20 minutes
Boil up plenty of salted water. Clean and wash the savoy cabbage and remove 6-8 large leaves. Cut out the thick end of the middle rib in each case. Cook the leaves in boiling water for 1-2 minutes. Quench and drain
Grate cheese. Heat the fat. Sweat flour in it until golden brown. Deglaze with stock and milk while stirring. Let simmer for about 5 minutes. Season to taste with salt, pepper and nutmeg. Melt half the cheese in the sauce
Salmon off the skin. Rinse with cold water and pat dry. Sprinkle the salmon with some lemon juice
Quench the potatoes and peel them. Cut the potatoes into slices
Layer half of the potato slices in a greased casserole dish (approx. 30 cm long). Pour 1/3 of the sauce over it. Then cover with half savoy cabbage leaves. Spread the second third of the sauce on top and cover with the salmon. Place the remaining savoy cabbage leaves on top and spread the remaining potato slices on top. Pour the rest of the sauce over it
Cook the casserole in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C / gas: level 3) for 40-45 minutes. After 20 minutes, sprinkle with remaining cheese and bake until done