Heat oil until smoking in a wok or large skillet over high heat. Stir-fry the onion for 1 minute, then add the ginger and garlic, and cook for 30 seconds more. Stir in the pork and cook for 2 minutes until browned. Then stir in the mushrooms and carrot; cook another two minutes.
Stir together the soy sauce, rice wine, sugar, and cornstarch in a small bowl. Pour into stir-fry, and bring to a boil. Cook for 30 seconds until the sauce has thickened, and has turned clear. Remove from the heat and transfer to a serving dish.