Chinese Beef and Onion Stir Fry

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)
1 tablespoon oil (added after marinating)
Sauce
1 tablespoon soy sauce (low sodium)
1 tablespoon corn starch
1 teaspoon sugar
1½ tablespoons oyster sauce
½ tablespoon hoisin sauce
1 teaspoon sesame oil
½ tablespoon Shaoxing cooking wine (or dry sherry/rice wine)
1 teaspoon dark soy sauce (for color, can sub with regular soy sauce)
½ cup water
Instructions:

Preparation
Peel and slice ½ white onion (or yellow onion), and separate the segments. Set it aside for later
Peel and thinly slice 3 cloves garlic. Alternatively, you can also mince it as well.
Slice 4-5 slices ginger and set it aside for later.
Cut off the root part of 1 stalk green onion and discard it. Then cut the green onion into 2-inch pieces. For the chonky white part, slice it in half lengthwise again. Set this aside for later.
Marinate Beef
Thinly slice the beef against the grain and put it in a bowl.
(Optional) To make it easier to slice, you can put it in the freezer for 15 minutes to firm it up slightly.