Place the packaged flank steak in the freezer for 1 hour ahead of cooking (or at least 30 minutes).

Slice the flank steak against the grain into strips as thinly as possible. Let the steak strips rest on the counter to remove the chill from the freezer while we prep the sauce and cook the broccoli.

In a medium bowl, whisk together all the sauce ingredients: ginger, garlic, chicken stock, soy sauce, brown sugar, sesame oil, sriracha, and cornstarch. Microwave for 40 seconds to dissolve the brown sugar.

Add two tablespoons of oil into a large skillet over medium-low heat. Add in the broccoli and saute about 2 minutes, flip, and add a few tablespoons of water into the pan. Partially cover with a lid and cook 2-3 more minutes. Remove and set aside under tented foil to keep warm.

Add another 1-2 tablespoons of oil. Heat to medium-high heat. Add the steak slices in a single layer. Work in batches to avoid overcrowding the pan resulting in steamed beef. Sear for 2 minutes per side. Reduce the heat to low.

Pour in the sauce and simmer until it begins to thicken, about 2 minutes. Add the broccoli back into the skillet and toss it all to evenly coat. Add sesame seeds and green onions if desired and serve over rice or noodles.