In a bowl, combine beef, cornstarch, and soy sauce. Toss together and let it rest for 20 minutes. This step is important as it helps to tenderize the beef and add flavor.

Mix all sauce ingredients in a small bowl. This will ensure that the sauce is well-combined before adding it to the stir-fry.

Heat 1 tablespoon oil in a large skillet over medium-high heat. Cook half of the beef until browned (about 4-5 minutes), then set aside. Repeat with the remaining beef. Make sure not to overcrowd the skillet, as this can prevent proper browning.

Reduce heat to medium, add 1 tablespoon oil to the skillet. Cook ginger, garlic, and the white parts of the onions until fragrant (about 1 minute). Stir frequently to avoid burning.

Add the white parts of the bok choy and cook for 2-3 minutes until slightly tender. This adds a nice crunch to your dish.

Stir in the sauce, bok choy greens, and beef. Cook until hot and bubbly (about 2-3 minutes). Stir gently to combine all ingredients evenly.

Remove from heat, garnish with green onion tops, and serve over rice for a complete meal. Enjoy the delicious flavors!