Heat the oil in a frying pan, brown the vegetable balls for approx. 3 mins. and remove. Toast the pitta breads in the same pan on both sides for approx. 1 min. each side, then halve lengthways. Mix together the sour half cream, ketchup, mayonnaise, lemon juice, chilli powder, salt and pepper. Divide the salad, tomatoes, sauce and vegetable balls into the pitta breads and serve.