Wash the potatoes and cook in boiling water for about 20 minutes. In the meantime cut broccoli florets from the stems and wash them. Peel, wash and slice the carrots. Cook broccoli and carrots in boiling salted water for about 5 minutes.
Finely grate the cheese. Peel onion and chop finely. Drain vegetables. Drain potatoes, rinse with cold water and peel. Cut potatoes into pieces. Peel sausage and cut into thin slices.
Heat the oil in a pan and sauté the onion. Dust with flour and sauté. Deglaze with stock and cream, bring to the boil and cook for about 5 minutes. Remove from the heat and melt 2/3 of the cheese in it while stirring.
Season to taste with salt, pepper and nutmeg. Spread potatoes, vegetables and sausage on a fat pan (33 x 27 cm). Pour sauce over it. Sprinkle the rest of the cheese on top. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for about 15 minutes.
Remove and serve immediately.