Why the plank? A smoldering cedar board imparts a warm, smoky flavor and retains the salmon's juiciness.
Arrange the cedar planks in a large baking dish. Cover with a few inches of water and then weight them down to keep them submerged. Let soak for 1 hour.
Meanwhile, in a medium saucepan, cook the curry paste and oil over medium heat, stirring constantly, until mixture is fragrant and bubbling, about 2 minutes. Stir in the chili sauce, Worcestershire sauce, sesame oil, and 1/3 cup water. Remove sauce from heat and let cool to room temperature.
Preheat the grill to medium-high. Sprinkle the salmon on both sides with the paprika, garlic powder, salt, and pepper. Drain planks and place on the grill. After 3 to 4 minutes, flip the planks over and top with the salmon.
Cover the grill and cook the salmon for 5 minutes. Uncover and brush with 1/2 cup of the sauce. Cover and cook for 10 minutes, then brush with another 1/2 cup of the sauce. Cook until the sides of the salmon are just opaque, about 4 minutes more. Brush with the remaining sauce.
Transfer the salmon to plates. Garnish with the scallion and sesame seeds.
Pro Check out your local lumberyard for high-quality untreated planks; they often cost less than the ones you’d find at a cooking store.