Prepare the Kroeung: In a mortar and pestle or food processor, combine lemongrass, garlic, shallots, galangal, kaffir lime leaves, chili peppers, turmeric powder, and shrimp paste. Pound or blend until a smooth paste forms.

In a mixing bowl, whisk together the eggs, fish sauce, and palm sugar until well combined. Stir in the Kroeung paste and coconut milk, mixing thoroughly.

Cut the fish fillets into bite-sized pieces and gently fold them into the coconut mixture, ensuring each piece is well coated.

If using banana leaves, soften them by briefly passing over an open flame or dipping in hot water to make them pliable. Cut into squares large enough to hold individual portions. Alternatively, use aluminum foil.

Place a portion of the fish mixture onto the center of each banana leaf square. Fold the edges to create a secure parcel, using toothpicks to fasten if necessary.

Arrange the parcels in a steamer basket and steam over boiling water for 20-25 minutes, or until the fish is cooked through and the mixture has set.

Serve the Amok Trey hot, garnished with additional kaffir lime leaves or red chili slices if desired.