Pat the salmon completely dry with paper towels. In a small bowl, whisk the miso, mirin, sake, soy sauce, honey, sesame oil, ginger, and garlic together until smooth, about the texture of loose peanut butter.
Set the fillets in a dish and spoon roughly two-thirds of the glaze over them, turning to coat. Reserve the rest for finishing. Let them sit at room temperature for 15 to 30 minutes, or cover and refrigerate up to overnight for a deeper cure.
Move an oven rack to about 6 inches below the broiler and heat the broiler to high. Line a sheet pan with foil and rub it with the neutral oil. Scrape most of the glaze off each fillet, since miso and honey scorch fast, and lay them skin side down.
Broil for 7 to 10 minutes, watching closely, until the tops are caramelized and the fish flakes at the thickest point. If the glaze darkens before the center is done, drop the rack a level. Thicker fillets take longer.
Spoon the reserved glaze over the hot fillets and rest 3 minutes. Top with scallions and sesame seeds and serve with lime wedges and rice.