Preheat a grill to high heat.
Combine the lemongrass, oil, shallots, galangal, oyster sauce, soy sauce, white pepper, coriander root, garlic and lime leaves in a blender or mortar and pestle to create a paste.
Place about a tablespoon of the paste onto each of 2 fish fillets. Close like a sandwich with the remaining fish fillets. Roll each "sandwich" in one of the banana leaves and wrap in foil. Grill for about 20 minutes total over medium heat.
NotesThis recipe was provided by a chef, restaurant or culinary professional and may have been scaled down from a bulk recipe. The Food Network Kitchens have not it for home use and therefore cannot make any representation as to the results.