Add a tbs of oil into a large saucepan, once hot add the curry paste mixture and cook for a few minutes until fragrant. Add the sweet potato and make sure to stir so they are covered evenly with the paste. Cook for a couple of minutes and then add the Coconut milk and Add half a cup of water. Bring to the boil then Reduce heat and let simmer for about 40 minutes. After about 10 minutes of the curry cooking add the salt, sugar, Bell Pepper, Lime Juice, soy sauce, fish sauce and Chopped Kaffir Lime Leaves to the curry. Give it a stir and let it simmer for the remaining time. If you like a good kick add 2 more chillies for extra heat.