In a medium mixing bowl, blend together the softened unsalted butter, white miso paste, brown sugar, grated fresh ginger, minced garlic, and sliced green onions until well combined and smooth.

Pat the fresh salmon fillets dry with paper towels. Divide the miso butter mixture evenly over each fillet, covering them fully.

Preheat your oven to 375°F (190°C). Arrange the salmon fillets in a greased baking dish and bake for 12 to 15 minutes until opaque.

Alternatively, preheat an air fryer to 400°F (200°C), line with parchment paper, and cook the salmon fillets for 9 to 10 minutes without flipping.

Transfer the cooked salmon to a serving platter, drizzle with remaining miso butter, and garnish with additional green onions and sesame seeds.