First make the marinade. In a large pestle and mortar, crush the garlic with the sea salt and black pepper, stir in the lemon juice, olive oil and spices. Pour this over chicken and coat well, marinate for an hour or overnight.
Fold chicken thigh in half and thread onto two skewers together - one will not be strong enough, repeat with remaining 11 until you form a solid chicken kebab.
Place on a hot griddle pan and sear on each side, transfer to a baking tray and finish in a pre-heated oven at 180°c / Gas 4 for 40 minutes. Reserve cooking juices and pour over the chicken before serving.
To serve use a fork to pull off each thigh, or stand kebab on a board and slice off meat using a sharp knife. Crush the garlic with tahini, water, cumin, lemon juice, yogurt. Season with salt. Serve the chicken with the tahini yogurt sauce, warm pita breads, shredded iceberg lettuce, tomato halves and cucumber.