Pour marinade ingredients directly into freezer bag and mix well. Add beef and massage in marinade. Marinate at room temperature for 30 minutes or refrigerate for 2-8 hours.
When ready to make Beef and Broccoli, whisk the sauce ingredients together in a small bowl.
In another small bowl, combine garlic, ginger, red pepper flakes and 1 teaspoon peanut oil. Set aside.
Drain excess marinade off of beef (if there is any).
*Work in 2 batches if your beef cannot fit in one layer.* Heat 1 1/2 teaspoons peanut oil/vegetable oil in a large nonstick skillet over high heat until very hot and sizzling. Add beef to the skillet and break up any clumps; cook without stirring for 1 minute, then stir and cook until beef is browned and almost cooked through, about 1-2 minutes (it will cook more in the sauce). Don’t overcook or it won’t be as tender! Transfer beef to a large plate and cover.
Add 1 tablespoon peanut oil/vegetable oil to the now-empty skillet; heat until very hot and sizzling. Add the broccoli and saute for 30 seconds. Add water, cover pan, and lower heat to medium. Steam broccoli until crisp-tender, about 2 minutes.
Push the broccoli to the sides of the skillet and add the garlic/ginger/red pepper/oil to the center of the pan, mashing the mixture with a spoon, until fragrant, about 15 to 20 seconds, then stir the mixture into the broccoli.
Return the beef to the skillet and toss to combine. Whisk the sauce to recombine then add to the skillet. Cook, stirring constantly, until the sauce is thickened and beef is cooked through, about 1-2 minutes. Transfer to a serving platter, sprinkle with the green onions and serve.