With your pan over a medium heat, add the coconut oil. When the oil is nice and hot, add the mustard seeds, fennel seeds and curry leaves.
As the mustard seeds start to pop, add the diced onion and salt and cook until the onion softens. This should take about 5 to 10 minutes.
Add the garlic, ginger and remaining spices. Cook out for a couple of minutes.
Add the chicken pieces and evenly coat them with the spicy onion mixture. Cook for 5 minutes, stirring occasionally.
Stir in the passata and water, place on the pan lid and cook for 30 minutes at a gentle simmer. Check the chicken pieces are thoroughly cooked and not pink in the centre.
Crumble in the coconut cream and stir until completely melted. If using coconut cream or milk, pour in and stir until fully incorporated.
Optional - sprinkle with toasted coconut flakes.
Serve with basmati rice and naan bread or roti.