For the mustard fondue, reduce veal and vegetable stock with crème fraîche and whipping cream by about a quarter over moderate heat. Add mustard of choice and continue cooking for a few minutes.
Meanwhile, skin the sausages and cut into 1-2 cm thick slices. Cut the pretzel sticks into narrow slices and fry in clarified butter until golden brown.
Season the mustard fondue with salt and pepper and decorate with lots of chopped parsley.
Serve the mustard fondue and heat the sausages on fondue forks in it.
Serve with slices of pretzel and pickles or cornichons.