chopped fresh Parsley (optional)
Mix together the mayonnaise, mustard, salt, lemon juice, and a few grinds of black pepper. Peel the celeriac and grate it coarsely. Mix the dressing with the celeriac and taste, adding additional salt, pepper, mustard, and lemon juice, to taste. Garnish with parsley if desired.
Note: If the salad is too thick, you can add a few spoonfuls of whole or low-fat milk to thin it out.