First make the red kroeung, by pounding the ingredients together in a mortar and pestle.
Heat oil in a wok over low heat. Add red kroeung, shrimp paste and palm sugar. Stir-fry until fragrant. Add the chicken pieces and cook until well coated and takes on a little colour. Then add the coconut cream and half the amount of fish sauce (you can add more later).
Stir in coconut milk and stock. Bring to the boil, then reduce heat and simmer over medium heat until chicken is tender. Add the long beans and aubergines. Just before serving add the potatoes and continue cooking until curry is reduced and thick. Taste, taste, taste, and if it's a little too mild in flavour (not heat) add more fish sauce.
Serve with steamed rice or fresh rice vermicelli and crunchy vegetables such as cucumber or bean sprouts. Cambodians also like to eat their curries with French baguettes.
Note: The curry will be tastier if you prepare this recipe using homemade coconut cream and milk. Also, while the curry paste will be bright red, the addition of the coconut cream and milk will see the curry have a yellow hue. This is not important, the flavour of the curry is.