Preheat the grill to a high heat. Cut the halloumi cheese into 8 thin slices and grill until golden on both sides.
Meanwhile, in a bowl mix together the spinach, watercress and rocket salad, cherry tomatoes, sugar snap peas and croutons.
For the dressing, mix together the Greek yogurt, lemon juice, 1tbsp of water, chopped basil and parsley.
Add the grilled cheese and dressing to the salad, toss gently and serve immediately.