Mash together softened butter, miso, rice vinegar, honey, and garlic until fully combined.
Pat salmon dry and season lightly with salt and pepper.
Heat oil in a large skillet over medium-high heat. Sear salmon for 3-4 minutes on the first side until golden-brown.
Flip the salmon and add the miso butter around the fillets. Baste continuously for 2-3 minutes until glossy and caramelized.
In the same skillet, add the whole scallions and cook for 2-3 minutes until charred and blistered.
Plate the salmon with the charred scallions, spoon over remaining browned butter, and finish with sesame seeds.