Slice the flank steak against the grain into thin, bite-sized strips.
Mince the garlic and finely grate the fresh ginger.
Heat the avocado oil in a large skillet or wok over medium-high heat until shimmering.
Add the beef strips to the pan in a single layer and sear until browned, about 2 minutes per side.
Remove the beef from the pan and set aside on a plate.
Add the broccoli florets and a splash of water to the pan, covering with a lid for 2 minutes to steam until bright green.
Return the beef to the pan and stir in the coconut aminos, toasted sesame oil, garlic, and ginger.
Season with sea salt and black pepper, tossing everything together for 1 minute until the sauce coats the ingredients.
Plate the stir-fry immediately and garnish with sesame seeds before serving.