Carefully loosen the skin from the breast side of the chicken. Mix the softened butter and preserved lemon together. With your fingers, place the butter mixture under the skin of the chicken, spreading out evenly.
Combine the ginger, cumin, coriander, chilli, and salt together, mix with oil and rub all over the chicken skin.
Place the chicken onto the BBQ, using an aluminium drip tray and cook for 60 mins.
Check the chicken is cooked by placing a skewer through the thickest part of the thigh and there are no pink juices.
Remove from BBQ and drizzle with pomegranate molasses. Cover with foil, allow to rest.
Toss sweet potato with the extra cumin and olive oil. Place on the grill and cook for 8 mins each side with the lid down, making sure they do not blacken.
Serve chicken with yogurt, mint leaves, and sweet potato.