Grind the chilies, shallots, belacan and lemongrass in a food processor to get a well blended and smooth.
Heat up a wok and stir-fry the sambal paste until aromatic or until the oil separates from the sambal paste.
Add the seasonings: salt, sugar, and fish sauce and stir. Dish out and set aside.
For The Dipping Sauce
Soak the tamarind pulp in water for 15 minutes and extract the juice.
Pound/blend the red chilies, bird’s eye chilies, and toasted belacan in a blender or a pestle and mortar.
Add tamarind juice, sugar, salt, and sliced shallots to the sambal. Stir well and set aside.
Grilling the Fish
Lay a few sheets of banana leaves and grease the surface of the banana leaves with some oil. Lay the fish fillet on top of the banana leaves and add about 2 – 3 tablespoons of sambal on top of the fish. Spread the sambal evenly.
Place the fish on top of the grill (upper rack with indirect heat) and cover the grill. Wait for approximately 8 minutes (depending on the heat) and flip the fish over to the other side. Add 2 – 3 more tablespoons of sambal on the other side of the fish. Cook for another 8 minutes or until the fish is cooked.
Transfer the fish and the banana leaves to the lower rack and grill for a couple of minutes with direct heat and cook until you smell the aroma of burnt banana leaves.
Serve immediately with sambal belacan and sliced shallots dip.