Clean the savoy cabbage, quarter it and remove the stalk. Cut the savoy cabbage into strips and wash. Peel, wash and slice the carrots. Peel and finely chop the onion. Fry the savoy cabbage, carrots and onion in 2 tablespoons of hot fat.
Mix the stock (up to 3 tablespoons), milk and mustard and pour over the vegetables. Cook for about 15 minutes. Stir the remaining stock and flour until smooth, add and simmer for about 5 minutes. Season vegetables with salt and pepper.
Bake Rösti on a baking tray in a preheated oven (electric oven: 225 ° C/ gas: level 4) for 12-15 minutes. Fry the fried sausages in the remaining fat while turning for approx. 7 minutes. Arrange vegetables with sausages and Rösti on a plate.
Garnish with parsley leaves.