Discard the hard part of the lemongrass and chop the soft core. Fry the lemongrass, chilli and and curry paste in oil until they are soft. Add the coconut milk and bring to a quick boil. Process in a blender with the Thai basil leaves and coriander. Dice the fat from the turbot and fry until it is crisp. Add the tomatoes and shiitake towards the end. Fry the fish for 30 seconds on each side in a hot pan. Whip the sauce into a foam and top the fish with the sauce and the crisp turbot fat mixture.