Mix together the fish sauce, sea salt and sugar, add the salmon and make sure it’s coated well, then refrigerate for about 30 minutes. Transfer the fish to a wire rack positioned over a bowl or tray and refrigerate, uncovered, for several hours, or overnight. This will allow the fish to dry out slightly. Remove the salmon from the fridge about 30 minutes before cooking.
Barbecue the fish over high heat for about 2 minutes on each side, or until the outside is charred but the inside is still rare, and rest for 5 minutes. Coarsely flake the fish.
Mix together the shallots, peanuts, herbs and garlic in a bowl, then gently fold in the fish. For the dressing, whisk together the sugars, lime juice, fish sauce and the chilli powder and drizzle over the salad. Sprinkle with the salmon roe and ground roast rice to serve.