Season the salmon with salt and pepper while bringing it to room temperature.
Prepare the veggies by halving the garlic, slicing spring onions thinly, and slicing the ginger.
Mix soy sauce, rice wine (cheongju), mirin, sugar, and ginger in a bowl.
Add cooking oil a pan (enough to cover the bottom, don't skimp!) and fry the salmon, skin side down, on medium heat for 1-2 minute or until the skin is crispy.
Add butter and garlic to the pan. Flip and sear the top of the filets, and also sides until just golden brown (takes additional 2-3 minutes).
Add in the sauce you made and let it reduce. If you have any green chili pepper (shishito pepper), throw them in now.
Continuously swirl around and/or baste the salmon with the sauce for a couple minutes, or until the sauce thickens enough to be coating the salmon.
Serve the salmon and spoon over any remainin sauce, and finish with a sprinkle of spring onions and sesame seeds on top.
