Make the honey-soy sauce: whisk together soy sauce, 3 tablespoons honey, sweet chili sauce, rice vinegar, hoisin sauce, hot chili sauce (to taste), garlic powder, ground ginger and onion powder in a medium bowl.
Reserve 1/4 cup of the sauce in a shallow dish for marinating; set the remainder aside for the glaze.
Add the salmon to the reserved 1/4 cup sauce in the shallow dish or a sealed bag and marinate 30–60 minutes at room temperature.
Preheat the oven to 400°F (200°C). Line a baking sheet with foil and spray with nonstick cooking spray.
Toss broccoli with 2 tablespoons olive oil, 1/2 tablespoon of the honey-soy sauce, 1/4 teaspoon salt and 1/8 teaspoon pepper; arrange in a single layer along one side of the prepared baking sheet.
Remove salmon from the marinade and pat dry with paper towels. Brush the top of each fillet with about 1 tablespoon honey total, then press the honeyed side into the chopped cashews so they adhere. Turn and press cashews into any bare spots.
Place the salmon fillets next to the broccoli on the baking sheet in a single layer.
Bake at 400°F for about 12–15 minutes, until salmon is cooked through and flakes easily with a fork (timing varies with thickness).
While the salmon finishes, make the glaze: add the reserved remaining sauce to a small saucepan and bring to a simmer until it thickly coats the back of a spoon, then stir in 1 tablespoon butter; simmer longer to thicken or add a splash of water if too thick.
Serve the salmon with the honey-soy glaze on the side or brushed lightly over the fillets; a little glaze goes a long way.
