To create the dill and turmeric marinade, wash, dry and peel the fresh turmeric knobs, chop roughly, and pound in a granite mortar with a pestle until completely crushed, then add salt, pepper, fresh dill, and one tablespoon of vegetable oil, and combine.
Cut the fish fillets into large pieces of around 5cm x 5cm or thereabouts. Transfer the dill and turmeric marinade to a bowl or plastic zip-log and add the fish pieces, ensuring they’re completely covered with the marinade, then refrigerate for a minimum of one hour to absorb the flavours.
Create a paste by pounding the garlic in the mortar, then add the shallots and pound, then add the chillies and pound, then set aside. Only add the birds-eye chilli if you like heat.
To a clay pot, small frying pan or small cooking pot, add the garlic, shallot and chilli paste, two tablespoons of vegetable oil, and pepper, stir to combine, then cook on low heat for a minute or so until aromatic and sizzling.
Sprinkle in the sugar, stir, and allow to caramelize for a minute or two. Then add the fish sauce, stir to combine, add the water and stir, then turn up the heat to bring to boil.
Once the sauce boils, turn the heat down. Try the sauce and adjust the seasoning to suit your taste, then add the fish pieces, and gently cook until just done.
Sprinkle chopped fresh dill, sliced spring onions or scallions, and roasted peanuts over the fish, put the lid on the clay pot to keep warm or transfer to a serving dish, and serve immediately with steamed rice or rice noodles, and more fresh dill.