Peel and finely chop the onion. Heat 1 tablespoon of fat in a pot. Sauté the onion until transparent. Add spinach and approx. 100 ml water, bring to the boil, cover and allow to defrost at low heat for approx. 15 minutes.
Season to taste with salt, pepper and nutmeg. Then bring to the boil again briefly, pour onto a sieve and drain. Melt 40 g fat in a pot. Stir in flour and sweat briefly. Add stock and milk while stirring.
Bring to the boil, cook for 3-5 minutes. Stir cream cheese into the sauce and season with salt and pepper. Wash marjoram, shake dry. Pluck the leaves from the stalks, except for a little bit for garnishing, and chop finely.
Squeeze the sausage meat out of the skin and season with marjoram. Pour into a freezer bag or disposable piping bag, cut off one corner of the bag and inject sausage meat into the cannelloni. Spread spinach in a greased rectangular casserole dish.
Place filled cannelloni on top. Pour sauce over it. Sprinkle with cheese and cook in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for 30-40 minutes. Garnish with marjoram and serve.