Gather all the ingredients.

For the seasonings, combine 1 tablespoon miso, 1 tablespoon sugar, 2 tablespoon sake, 1 tablespoon mirin, and 1½ tablespoon soy sauce. Mix well and set aside.

Finely chop some chives and cut off the stems of ½ package shimeji (brown beech) mushrooms. Separate the shimeji into smaller clusters with your hands.

Cut off the stems of 2 shiitake mushrooms and thinly slice them.

Check to see if your salmon has any bones and remove if there are any. Pat dry 2 fillets skin-on salmon fillets with a paper towel and season it with Diamond Crystal kosher salt and freshly ground black pepper.

Sprinkle ½ tablespoon all-purpose flour (plain flour) on the salmon and thinly coat it all over.

Heat a frying pan over medium heat. When the pan is hot, add 1 tablespoon neutral oil. Place the salmon in the pan, flesh side down. Cook for 5 minutes.

Flip the fillets over so the skin side is on the bottom. Then, add the shimeji and shiitake mushrooms. Cook the skin side for 5 minutes.

Next, cook the sides of the salmon fillets for 1 minute each.

Add 1 tablespoon unsalted butter and sauté the mushrooms. Put the mushrooms on top of the salmon.

Add the seasonings mixture to the pan. Coat the salmon with the sauce using a spoon.

Transfer the salmon and mushrooms to individual plates. Spoon some pan sauce on top and garnish with the chopped chives and toasted white sesame seeds.

You can store the leftovers in an airtight container and keep in the refrigerator for up to 3 days or in the freezer for a month.