Heat oil in a wok or large skillet over medium-high heat. Add meat and stir-fry 1 minute. Add soy sauce and next 5 ingredients. Stir-fry 2 minutes more. Add prepared wasabi to taste, start with 1 teaspoon and add more to taste. Add onions and mango and cook 30 seconds more. Mound rice on plates and spoon duck mixture over.