Fresh red cabbage salad with feta and apple

Difficulty:  Time: INGREDIENTS (x4 persons): - 25 g of walnuts - ½ red cabbage finely shredded - 2 sticks celery, sliced - 2 Pink lady apples, thinly sliced - 150 g Greek feta, crumbled - 1/2 red onion, thinly sliced (optional) DRESSING - 2 tbsp wholegrain mustard with honey - 2 tbsp extra virgin olive oil - 1 tbsp lemon juice - salt/pepper ...