Peel, wash and quarter the potatoes. Clean and wash the Brussels sprouts and cut the stalk into wedges. Cook cabbage and potatoes in boiling salted water for about 20 minutes, then drain.
Add milk and butter and mash. Season to taste with salt, pepper and nutmeg. Meanwhile, wash the cured pork loin and pat dry. Peel onions and cut into rings. Heat 1 teaspoon of oil in a large pan.
Fry the onions in it until golden brown and take them out. Add 1 teaspoon of oil to the frying fat. Fry the smoked pork on each side for about 3 minutes. Season with pepper and take out. Deglaze the meat with 250 ml water, bring to the boil and stir in the stock.
Refine with cream. Season with salt, pepper, thyme and mustard. Stir in the sauce thickener, bring to the boil again. Arrange on plates garnished with thyme.