Wash the potatoes thoroughly, peel and dice them. Wash again if necessary. Peel and finely dice the onion. Press the sausage meat out of the skin as a dumpling. Heat the oil in a pan and fry the dumplings for about 3 minutes, turning them over at medium heat.
Remove from the pan. Add potatoes to the frying fat and fry for 8-10 minutes, turning several times. In the meantime clean, wash and slice the zucchini. Add the onion to the potatoes and fry briefly.
Season with salt and pepper. Remove from the pan. Add the zucchini to the frying fat and fry for 3-4 minutes while turning. Add potatoes and dumplings. Deglaze with stock and cream and simmer for 4-5 minutes.
Stir in the sauce thickener, bring to the boil again and season to taste with salt and pepper. Serve garnished with chervil.