teriyaki salmon recipe

4 salmon fillets 1/4 cup soy sauce 1/4 cup mirin (Japanese sweet rice wine) or honey 2 tablespoons rice vinegar 2 tablespoons brown sugar 1 teaspoon grated ginger 2 cloves garlic, minced 1 tablespoon cornstarch 1/4 cup water 1 tablespoon sesame oil (optional for garnish)