potato salad

Name: potato salad
Ingredients: 1kg Jersey Royals or new potatoes, scrubbed and halved; 3 red apples, cored and cut into thin wedges; 4 celery sticks, thinly sliced; For the dressing:; 300g fat free natural fromage frais; ½ tsp mustard powder; 1 tbsp cider vinegar; Bunch of spring onions, thinly sliced; Small handful of finely chopped fresh dill; Small handful of finely chopped fresh chives; Salt and freshly ground black pepper