In a bowl, combine the soy sauce, mirin, honey (or brown sugar), rice vinegar, minced garlic, and grated ginger. Whisk the ingredients together until well combined.
Place the salmon fillets in a shallow dish or a resealable plastic bag. Pour the teriyaki marinade over the salmon, ensuring it covers the fillets completely. Allow the salmon to marinate in the refrigerator for at least 30 minutes. For enhanced flavor, you can marinate it for up to 4 hours.
Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper or lightly grease it to prevent sticking.
Remove the salmon from the marinade, reserving the excess marinade for later use. Place the salmon fillets on the prepared baking sheet. Bake for approximately 10-15 minutes, or until the salmon is cooked through and flakes easily with a fork. Cooking time may vary depending on the thickness of the fillets.
While the salmon is baking, pour the reserved marinade into a small saucepan. Bring the mixture to a boil over medium heat, then reduce the heat to low. In a separate bowl, mix the cornstarch with water to create a slurry, and slowly add it to the saucepan, stirring constantly until the sauce thickens slightly. Remove from heat.
Once the salmon is cooked, brush the teriyaki glaze generously over each fillet. You can reserve some glaze for drizzling over the salmon when serving.
Transfer the teriyaki salmon to a serving plate or individual plates. Sprinkle sesame seeds and sliced green onions on top for added visual appeal and flavor. Pair it with steamed rice and your choice of vegetables for a complete meal.