Peel the mango. Cut half into small dice and set aside for folding through the chicken. Puree the remaining half with a splash of water till smooth. Sauté the onion in a little olive oil till soft. Add the curry spices and stir to toast them briefly. Add the tomato puree and the pureed mango. Stir till smooth then remove from the heat and leave to cool.

Once the sauce is cooled stir in the yogurt and lemon juice to create a smooth sauce. Fold in the chopped coriander, chicken and diced mango. Once ready to serve lay the cos leaves and celery out on a large platter and spoon the chicken onto the platter or into a separate bowl. Scatter with the nigella seeds and pomegranate arils. Serve immediately.