Start by making the Cambodian-style kroeung spice paste.
Combine the lemongrass, garlic, shallots, turmeric, galangal, and kaffir lime leavesin a food processor or grind up the ingredients using a mortar and pestle. Grind until you get a fine paste--This is your kroeung spice paste.
In a bowl, combine the kroeung with the coconut milk, eggs, fish sauce, sugar, and a pinch of Kosher salt.
Mix until well combined.
Add the Sea Bass pieces to the bowl, and gently mix until they're well coated with the curry mixture.
Let this mixture sit for about 15 minutes to allow the fish time to marinate slightly.
While the fish is marinating, prepare your steamer and banana leaf cups.
You can make the cups by folding the banana leaves into a square or a round shape and securing them with toothpicks.
Divide the fish along with the curry mixture evenly among the banana leaf cups.
Top each with a few Thai basil leaves.
Steam the filled banana leaf cups for about 20-25 minutes, or until the curry mixture is firm and the fish is cooked through.
Once done, remove from the steamer and let them cool slightly before serving. Serve your Amok Trei with steamed basmati rice on the side.