1.Preheat oven to 180°C/350°F.
2.Place unpeeled garlic on a baking tray; drizzle with oil. Roast for 10 minutes. When cool enough to handle, peel garlic and place in a small bowl; mash with a fork. Add yoghurt; stir to combine.
3.Cook lamb on a heated oiled grill plate (or grill or barbecue) for 4 minutes each side or until cooked as desired. Remove from heat; cover to keep warm.
4.Make za’atar. Dry-fry sesame seeds in a small frying pan, shaking pan until seeds are golden. Add sumac; shake pan until fragrant. Transfer to a small bowl; stir in thyme and oil.
5.Toss lamb in za’atar to coat. Season to taste.
6.Serve lamb with parsley; accompany with garlic yoghurt, and lemon cheeks.