Thinly slice the leek, dice the celeriac and carrots. Heat the butter in a pan, sauté the vegetables for approx. 3 mins., add the barley, cook briefly.
Pour in the stock, bring to the boil, cover and simmer over a low heat for approx. 45 mins., season.
Cut the frankfurters diagonally into pieces, add to the soup along with the single cream, heat gently. Plate up the soup and garnish with the finely chopped chives.