In a medium bowl, combine soy sauce, rice wine, sugar, and 1/4 cup of water, whisking until the sugar dissolves. In a saucepan over medium heat, add 1 tablespoon of oil, and sauté finely chopped spring onion, ginger, and garlic until lightly browned, about 2-3 minutes. Pour the sauce mixture into the pan, cover, and simmer for 5 minutes until fragrant. Remove from heat, drain, and set the soy glaze aside.

Fill a medium saucepan with water, ensuring it’s deep enough for the fish to be submerged (about 5-10 cm above the fillets). Bring the water to a rolling boil over high heat. Once boiling, lower the heat to a gentle simmer.

Carefully slide the fish fillets into the simmering water, ensuring they are completely submerged. Cook for 1 minute, then turn off the heat and cover the saucepan with a lid. Let the fish poach gently for 5-7 minutes.

In a small skillet, heat 3 tablespoons of oil along with sesame seeds over medium heat until the seeds turn light brown and pop, about 1-2 minutes. Remove from heat and pour this fragrant oil over the poached fish. Sprinkle with the reserved chopped spring onions, then generously drizzle the warm soy glaze over everything.