Brine the salmon* (optional): In a shallow dish whisk together 4 cups room temperature water and 3 tablespoons kosher salt until it dissolves. Place the salmon in the water and wait for 15 minutes.
Preheat the broiler to high.
Make the glaze: Meanwhile, in a small bowl, stir together the miso, honey, soy sauce, rice wine, garlic powder, and ground ginger.
Prepare the salmon: Place a large sheet of aluminum foil on a baking sheet and brush it with olive oil. Pat each piece of salmon dry and place it on the foil skin side down. Brush the salmon with a bit of the olive oil and sprinkle with the ½ teaspoon kosher salt evenly divided among the fillets. Reserve about half of the glaze and brush the remainder on the salmon.
Broil the salmon: Broil 7 to 10 minutes for 1-inch thick salmon (or less for thinner fish), until it’s just tender and pink at the center (the internal temperature should be between 125 to 130°F in the center). Pour the reserved glaze onto the salmon and garnish with the parsley, if using. Serve immediately. Leftovers last refrigerated for up to 3 days.