In a glass baking dish, mix together the malt vinegar, curd, olive oil, mixed spice, cardamom, salt and pepper. Place the chicken thighs into the mixture and turn to coat. Cover and marinate in the refrigerator for at least 4 hours or overnight.
In a small bowl, mix together the tahini, curd, garlic, lemon juice, olive oil and parsley. Season with salt and pepper, taste, and adjust flavours if desired. Cover and refrigerate.
Preheat the oven to 175 C. Cover the chicken with foil and bake in the marinade for 30 minutes, turning once. Uncover, and cook for an additional 5 to 10 minutes, or until chicken is browned and cooked through. Remove from the dish, and cut into thin slices.
Place sliced chicken, tomato, onion and lettuce onto pitta breads. Roll up, and top with the tahini sauce.