Heat wok over a high heat. Add peanut oil. Add onion. Stir-fry for 3 mins or until softened. Add chicken. Stir fry for 3 mins, or until browned & cooked. Add curry paste. Cook for 1 min or until fragrant.
Add coconut milk and stock. Bring to the boil. Reduce heat to medium. Simmer for 5-7 mins or until sauce thickens and chicken is cooked. Add fish sauce, brown sugar and pineapple. Simmer for 2 mins or until heated through.
Spoon curry into bowls and you can garnish with fried shallots and fresh coriander. Serve with rice.