Soak the dried goraka in ¾ cup warm water for about 1 hour until softened.
Transfer the soaked goraka (along with the soaking water) to a blender.
Add the garlic, ginger, black pepper powder, turmeric powder and salt.
Blend into a thick, smooth paste.
Place the tuna pieces in a large bowl.
Coat each piece thoroughly with the prepared goraka paste.
Marinate for 30 minutes to 1 hour.
In a heavy-bottomed pot, arrange Curry leaves, Pandan pieces, Crushed cinnamon, Slit green chillies.
Place the marinated fish pieces over the aromatics in a single layer.
Spread any remaining marinade over the fish.
Pour ⅓ cup water around the edges of the pot.
Top with a few extra curry leaves and pandan pieces.
Cover the pot with a lid.
Cook over low heat.
Do not stir, as the fish can easily break apart.
Occasionally swirl the pot gently if needed.
Cook for about 45–60 minutes, or until the fish is fully cooked, the gravy has reduced and the curry is almost dry, with the spices coating each piece of fish.
Allow the Ambual Thiyal to rest for 10–15 minutes before serving.
Serve with Steamed rice, Sri Lankan dhal curry, Pol sambol, Gotu kola sambol, Fried papadums.