Make the marinade by mixing together the sugar, salt, soy sauce and cornflour slurry. Mix in the pork, let marinate for 15 minutes.
Cut off the enoki mushroom root, set it aside.
Make the sauce by combining 2 tablespoons cooking sake, 1 tablespoon caster sugar, 4 teaspoons tamari, 1 tablespoon mirin and 1 tablespoon ginger in a bowl.
Heat a large frying pan with 1 tablespoon oil over high heat. Stir-fry the 1/2 tablespoon garlic until fragrant, 2-3 minutes. Stir-fry the pork until done, about 3-4 minutes. Set aside.
In the same frying pan, heat 1 tablespoon oil over high heat. Stir-fry the onion with some salt until fragrant and soft, about 2-3 minutes. Add the pork back into the pan and mix well. Add the sauce and enoki mushrooms, stir well to combine. Scatter over nori sheets and serve.