Pat salmon dry with paper towels. Season with salt and pepper to taste. Set aside.
Adjust the oven rack to the middle position. Preheat the broiler. In a small bowl, whisk together the garlic, brown sugar, bourbon, soy sauce, and green onions.
Add the butter and oil to a large, oven-safe skillet (at least 12 inches) over medium-high heat. Once the butter melts, whisk in the bourbon mixture. Bring to a boil over medium-high heat and cook, whisking constantly, for about 1-2 minutes. Add the salmon, skin side down (if using salmon with skin); cook for 3 minutes. Baste the salmon with the sauce by spooning the sauce over the salmon periodically as it cooks.
Transfer the skillet to the middle rack under the broiler. Broil salmon for 5-6 minutes, basting with the bourbon glaze about halfway through, until the salmon is caramelized on top and the fish flakes easily with a fork.
Notes
If you’re starting with frozen salmon, let the salmon thaw in the refrigerator overnight before using in this recipe.
Pat the fish dry with paper towels before seasoning.
Use a cast iron skillet that's at least 12-inches in diameter. This allows for plenty of space in between salmon fillets, which helps the fish cook evenly and crisp on the edges (rather than steam). This is the skillet shown here.
If you don't have an oven-proof skillet, transfer the salmon and the glaze to a baking dish or other oven-safe pan before placing it under the broiler.
Broil the fish on the middle rack in the oven. If the salmon is on the top rack (closest to the broiler flame), the glaze will burn before the fish cooks through.
The total cooking time will vary depending on the size, temperature, and thickness of your fish when it goes under the broiler. As a result, keep a close eye on the salmon and remove it as soon as the outside is crisp and the inside flakes easily with a fork. If using a meat thermometer, you’re looking for an internal temperature of 145°F in the thickest part of the fish.