Mix the miso, sake, honey, mirin, and soy sauce in a large flat dish (such as a pie pan) or a large resealable plastic bag. Optionally, you can taste the marinade and add more ingredients to taste if you prefer more honey, etc.
Add the salmon, making sure the fish is coated with the marinade.
Cover and marinate at room temperature for at least 30 minutes to one hour.
Place an oven rack near the top and preheat the broiler. Line a broiling pan with aluminum foil. Spray with cooking spray or brush some olive oil over the foil, then lay the salmon fillets on top, skin-side down, so they’re not touching. Brush a thin coating of marinade on top of the salmon.
Broil for 6-10 minutes, depending on how thick the fillets are and how hot your broiler is. Broilers vary in heat intensity, so keep an eye on the salmon to make sure the tops don’t burn. A little char is fine.
Transfer to dinner plates. Serve with rice and vegetables, topped with sliced scallion. Enjoy any leftovers within 3 days.
This salmon is excellent the next day over salad. I serve it chilled or at room temperature. This prevents the salmon from overcooking on reheat.