Position an oven rack about 8 inches away from the broiler element and heat the broiler to high.
Oil a large, rimmed baking sheet. Set the salmon skin side down on the baking sheet, sprinkle with 1 Tbs. oil, the coriander, 1/2 tsp. salt, and 1/2 tsp. pepper, and let sit at room temperature while you prepare the sauce.
In a large (12-inch) skillet over medium heat, cook the red pepper, scallion whites, and ginger in the remaining 2 Tbs. oil, stirring occasionally, until the red pepper and scallions start to soften and brown, about 3 minutes. Add the mushrooms, raise the heat to medium-high, sprinkle with 1/4 tsp. salt, and cook, stirring, until they soften and start to brown, about 3 minutes. Add the honey, vinegar, soy sauce, chili sauce, and 1/4 cup water, and bring to a simmer. Whisk the cornstarch with 1 tsp. water and stir into the glaze. Return to a simmer and cook until the glaze thickens, about 1 minute. Remove from the heat.
Broil the salmon until it starts to brown and becomes almost firm to the touch, about 8 minutes. Momentarily transfer to the stovetop and spoon the glaze over the salmon. Return to the oven and broil for about 1 more minute so the glaze browns and the salmon almost completely cooks through (check by using a paring knife to flake a thicker part of the fillet). Sprinkle with the scallion greens, transfer to a large platter, and serve.