The potatoes must still be warm. Mix up the dressing ingredients (mustard, vinegar, oil, gravy, nutmeg, some broth). Mix carefully with potatoes, onions and endive salad.
Admit so much broth that the whole thing becomes nice and mushy, but does not float.
Season to taste with salt and pepper.
Serve immediately.
Very tasty with Gschwollenen (naked sausages).
Tip: Instead of endive salad, you can also add cucumber sliced very thinly.