Bring ¼ cup of coconut milk to the boil in a pot or deep sauté pan.
Add curry paste and cook for 5 minutes until the oils separate. Now add remaining coconut milk, sugar, fish sauce and tamarind paste.
Add chicken, potatoes and onions and ¾ of a cup of water. Cook with the lid on for 35-40 minutes on a medium to low heat until chicken is almost falling from bone and potatoes are tender.