Celeriac salad

Ingredients

• 1 celeriac, peeled
• 1 bunch of fresh flat-leaf parsley
• 2 anchovies, finely chopped
• 2 heaped tablespoons good capers, finely chopped
• 2 heaped tablespoons small sweet and sour gherkins, finely chopped
• 5 tablespoons fat free natural yoghurt
• 1 heaped tablespoon Dijon mustard
• 3 tablespoons extra virgin olive oil
• 2-3 tablespoons sherry, red or white wine vinegar