Heat the coconut oil in a large saucepan and add the onion, garlic, chili, ginger and leek. Gently fry until the veggies soften. Stir in the curry paste, then pour in the stock and mussels. Bring to a boil and simmer for 6-7 minutes until the mussels open. Pour in the coconut milk, add the cilantro, heat through and serve.