Let the dumplings swell in a pot with plenty of cold salt water for about 10 minutes. Clean, wash and halve or quarter the mushrooms. Clean the leek, wash and cut into rings
Cut the sausages into diagonal slices and fry them in hot oil. Fry the mushrooms and leek briefly. Bring dumplings to the boil and let them simmer at low heat for about 10 minutes
Pour milk and 1/4 l water into the pan, bring to the boil and simmer for 3-4 minutes. Wash and chop the parsley. Thicken sauce with sauce thickener. Season to taste with mustard, salt and pepper
Lift out the dumplings, quench. Open the cooking bag and let the dumplings slide onto plates. Arrange with the ragout and sprinkle with parsley