Peel a head of Celariac and cut it into thin match stick pieces.
Bring a large saucepan of water (to which you have added 1 tbs Vinegar ) to the boil.
Plunge in the Celariac.
Bring back to the boil and then drain and cool under running water.
Add 2 teaspoons of mustard to 10 oz. of Mayonnaise and mix with the blanched Celariac.