1.Cut chicken in half horizontally. Place chicken in a medium bowl with za’atar and oil; toss to coat.
2.Cook chicken on a heated grill plate (or grill or barbecue), in batches, over medium heat for 2 minutes each side or until cooked through.
3.Meanwhile, make haloumi and watermelon salad. Combine vinegar, oil, garlic and sugar in a large bowl. Combine haloumi, za’atar and extra oil in a small bowl. Heat a medium frying pan over high heat; cook haloumi mixture for 2 minutes or until golden all over. Add haloumi to large bowl with watermelon, olives and mint; toss gently to combine.
4.Serve sliced chicken with salad.
The salad can be prepared several hours ahead; cook the haloumi and add the dressing just before serving. Haloumi is a semi-firm cheese with a spongy texture and a very salty sweet flavour. It is best grilled or fried, and holds its shape well on being heated. Eat while still warm as it becomes tough and rubbery on cooling.