Chinese Beef and Onion Stir Fry

Ingredients

300 g sirloin steak (or rib eye, flank steak or blade steak)
½ white onion (or yellow onion)
4-5 slices ginger
3 cloves garlic (minced or sliced thinly)
1 stalk green onion (cut into 2 inch pieces)
Marinade
1 tablespoon soy sauce
½ tablespoon Shaoxing cooking wine
2 tablespoons water
1 teaspoon sesame oil
1 teaspoon cornstarch (added after marinating)