In a mortar and pestle, crush salt, coriander and black peppercorns until finely ground. Alternatively, use a spice grinder.
Season fish all over with salt mixture. Make sure to season inside the cavity. Set aside and prepare sauce.
Char peppers over open flame or torch until completely black. Place in a bowl and cover for at least 10 minutes to steam. Once peppers feel softened, peel and discard char, seeds and stem from the peppers.
While peppers steam, in a pan cook the white parts of the scallions, shallots, garlic and ginger in some oil until softened. About 5 minutes.
Add peppers, scallion shallot mixture, tamarind concentrate, rice vinegar, water, fish sauce, soy sauce and honey to a blender. Process until smooth. Add 1 Tbsp of more water at a time to thin if the mixture is too thick. Sauce should have a loose mayo consistency. Adjust sauce with salt and black pepper to taste. Set sauce aside.
In a cast iron or heavy bottom pot large enough to fit fish in, pour about 1 inch of oil. Leave about 1-2 inches free from top of pot to avoid oil overflow. Heat oil to ~325F.
Dredge whole fish in rice flour until completely covered and coated.
Carefully put fish into oil and fry on on one side until crispy and golden. About 4 minutes. Carefully flip fish over and fry until golden. Another 4 minutes.
Remove fish from pot and place on a sheet tray with a wired rack. Top with flake salt.
Top fish with sliced scallion greens, sliced jalapeños and fresnos. Serve with cooked jasmine rice. Enjoy!
