Slice the flank steak against the grain into very thin strips to ensure maximum tenderness.
Season the beef strips evenly with the sea salt and black pepper.
Heat the avocado oil in a large wok or skillet over high heat until shimmering.
Add the beef in a single layer and sear for 1-2 minutes until browned and caramelized, then remove the beef from the pan and set aside.
In the same pan, add the sesame oil, minced garlic, and grated ginger, sautéing for 30 seconds until fragrant.
Toss in the broccoli florets and a splash of water, then cover the pan for 2 minutes to steam the broccoli until bright green and crisp-tender.
Return the beef to the pan, pour in the tamari, and toss everything together for 1 minute to glaze the ingredients.
Serve immediately while hot, garnished with the toasted sesame seeds.