Place the sliced flank steak in a larger bowl.
To the steak, add low sodium soy sauce, dry sherry, water, sesame seed oil, and cornstarch; toss to combine. Set aside for 15 minutes.
In the meantime, bring a pot of water to a boil; add the broccoli florets to the boiling water and cook for about 2 to 3 minutes, or until just tender. Drain, rinse, and set aside.
Cook the noodles according to the package directions. Rinse them with cold water and then toss the noodles with a drizzle of oil to prevent them from sticking. Set aside.
Add 1 tablespoon vegetable oil to a wok or a large skillet; set over high heat and heat it up.
To the hot oil, add the steak and cook for 1 minute per side.
Remove steak from the wok/pan.
Return pan to the burner and heat up 1 tablespoon vegetable oil and 1 tablespoon sesame seed oil.
Add ginger to the heated oil and cook for 5 seconds.
Stir in the garlic and cook for 10 seconds.
Stir in the sliced yellow onion and cook for 20 seconds.
Add in the cooked noodles; toss around and cook for a minute.
Make the stir fry sauce: In a small bowl whisk together 3 tablespoons soy sauce with 1 tablespoon dry sherry and a pinch of sugar.
Add the beef to the skillet and pour in the prepared stir fry sauce; stir to combine.
Stir in the bean sprouts, broccoli, and green onions; toss and stir, and cook for 30 seconds.
Remove from heat; taste and adjust accordingly.
Transfer everything to a serving plate.