Add as much dressing as you like to the celeriac and mix well.
Serve cold, though this salad can be kept in the fridge, covered with plastic film.
Remarks
With the amounts given, you will undoubtedly have more rémoulade dressing than you need, as it is difficult to give proportions for less than a whole egg. But don't worry, like mayonnaise, this keeps well and for as long.
Could you fancy adding an exotic touch to this recipe? Try using lime juice instead of lemon, or even bergamot.