In a mortar, pound the lemongrass, kaffir lime leaves, galangal, turmeric, garlic and salt into a fine paste. This is called the kroeung.
If you are using a food processor, put the easiest-to-grind ingredients in first. The liquid that forms will help to process the other harder-to-blend ingredients or add a few teaspoons of water to make the blending easier.
Add shrimp paste and dried chili. Continue to pound until well mixed. Put aside.
If you want to serve the Amok in a traditional fashion, take a large banana leaf and cut out 4 square pieces of 20 cm each. Place all the leaves together and cut off the corner tips diagonally. Each dish container will need two squares to prevent the mixture from leaking when steaming. Place two squares together and fold the long sides up about 3 cm to pleat and make a corner. Using a short toothpick, pin both the folded parts together. Repeat this for all sides of the leaves until you get a square bowl.
In a wok, heat up the vegetable oil. Add chopped garlic and shallot, stirring until fragrant.
Add the kroeung and 3 tablespoons of coconut cream. Then add the palm sugar, fish sauce, salt, chicken powder and fish. Cook for about a minute, add the remaining coconut cream (keep one tablespoon for the final garnish) and stir until it thickens and reaches boiling point. Remove from the heat and set aside.
Place nhor leaves at the bottom of each serving bowl. Pour the cooked fish mixture over and add the egg yolk. Pour the remaining coconut cream and top the dish with thinly sliced kaffir lime leafs and cayenne pepper.
In a steamer, place the Amok mixture and steam for 7-10 minutes.
Serve immediately with steamed rice or bread.