In a small bowl, mix soy sauce, sesame oil, mirin, brown sugar, sea salt, ginger powder, and optional chili flakes or chili oil.
1 tablespoon soy sauce, 1 tablespoon toasted sesame oil, ½ tablespoon mirin, 1 teaspoon brown sugar, Pinch of sea salt, ½ teaspoon ground ginger powder, 1 tsp chili flakes and chili oil