Mix ginger, soy sauce, 1/8 cup water, rice wine vinegar, sesame oil, brown sugar and garlic together in a medium sized bowl.
Place half of the marinade in a small saucepan and set aside. Put the other half in a Ziploc bag with the salmon and marinate for 30 minutes.
Use a large skillet to heat the oil. Add salmon filets so they are not overcrowding the pan. Cook two at a time if you have to.
Cook each filet for 3-4 minutes on each side.
In the meantime, heat the marinade you set aside in the saucepan bringing it to a simmer. Combine cornstarch and water in a small bowl and whisk to combine. Then whisk the cornstarch mixture into the marinade and simmer until it thickens.
Place salmon on a plate and drizzle with teriyaki sauce. Garnish with sesame seed and green onion garnish if desired.