Serves 4

450 g or 1 medium-sized celeriac

1/2 tbsp salt

1/2 tbsp lemon juice

4 tbsp French mustard

3 tbsp boiling water

scant 1/2 (us) cup (100 ml) olive oil or as needed

2 tbsp white vinegar

salt and pepper

for the garnish

2 tbsp chopped mixed herbs or parsley

1. Peel the celeriac, and cut it into matchsticks.

2. Toss the sticks in a bowl with the salt and lemon juice, and leave to stand for 30 minutes.

3. Rinse in a strainer under cold running water, drain well, and pat dry.

4. Put the mustard into a warmed bowl, and very gradually whisk in the boiling water.

5. Then whisk in the oil drop by drop as when making mayonnaise using enough to make a thick sauce.

6. Whisk in the vinegar in the same way. Season with salt and pepper.

7. Fold in the celeriac matchsticks, cover loosely with a cloth, and leave in a cool place for several hours or overnight.

8. Sprinkle the herbs over the dish before serving.