Begin by preparing the fish. In a large pot, add the water and bring it to a boil. Place the cleaned mackerel in the pot along with the bruised lemongrass. Simmer for 15 minutes or until the fish is cooked through. Remove the fish, set aside, and strain the broth to ensure clarity. Reserve the broth for later use.
Once the fish has cooled, carefully separate the flesh from the bones. Flake the flesh into small pieces, ensuring no bones remain. Return the fish bones to the reserved broth and simmer for another 10 minutes to extract maximum flavour. Strain again and set the enriched broth aside.
Prepare the spice paste. In a blender, combine the dried and fresh chilies, shallots, garlic, galangal, turmeric, and belacan. Blend into a smooth paste, adding a small amount of water if needed to ease blending. This paste forms the aromatic base of your soup.
In a large pot, heat 2 tablespoons of oil over medium heat. Fry the spice paste until fragrant, about 5–7 minutes, stirring constantly to prevent burning. Add the tamarind peel and dissolved tamarind paste to the pot, allowing the flavours to meld.
Pour the reserved fish broth into the pot with the spice paste. Stir well to combine. Add the flaked fish, fish sauce, and sugar. Adjust the seasoning as needed, balancing the sour, salty, and slightly sweet flavours characteristic of Asam Laksa. Simmer for 15 minutes.
While the soup simmers, prepare the noodles and garnishes. Cook the laksa noodles as per package instructions, rinse under cold water, and drain. Arrange cucumber, pineapple, red onion, mint leaves, and torch ginger flower (if using) on a serving platter for easy assembly.
Check the soup for final adjustments. Ensure the flavours are robust and balanced, with a pronounced tanginess from the tamarind. Remove from heat and keep warm.
To serve, divide the cooked noodles into individual bowls. Ladle the hot Asam Laksa broth generously over the noodles. Top with the prepared garnishes, drizzle with shrimp paste, and squeeze a wedge of lime over the dish. Serve immediately with extra lime and bird’s eye chilies for those who prefer more heat.