Slice the flank steak against the grain into thin strips and season evenly with the sea salt and black pepper.
In a small bowl, whisk together the tamari, honey, minced fresh ginger, and minced garlic to create the stir-fry glaze.
Heat the toasted sesame oil in a large skillet or wok over medium-high heat until it begins to shimmer.
Add the beef strips in a single layer and sear for 2 minutes per side until deeply browned and caramelized, then transfer the beef to a plate.
Add the broccoli florets to the same pan with a splash of water, cover immediately, and steam for 3 minutes until vibrant green and tender-crisp.
Return the beef and any accumulated juices to the pan, then pour in the tamari sauce mixture.
Toss everything together for 1 minute over high heat until the sauce thickens and coats the beef and broccoli.
Transfer the stir-fry to a serving plate and garnish with the toasted sesame seeds.