Slice the flank steak against the grain into thin, bite-sized strips to ensure maximum tenderness.
In a small bowl, whisk together the coconut aminos, arrowroot powder, minced garlic, and grated fresh ginger until smooth.
Heat the toasted sesame oil in a large skillet or wok over medium-high heat until shimmering.
Add the beef strips to the pan in a single layer, seasoning with sea salt and black pepper, and sear for 2 minutes until browned.
Toss in the broccoli florets along with 2 tablespoons of water, then cover the pan for 3 minutes to steam the broccoli until bright green.
Remove the lid, pour the prepared sauce over the beef and broccoli, and stir-fry for 1-2 minutes until the glaze thickens and coats everything beautifully.
Transfer to a plate and garnish with toasted sesame seeds before serving.