In a large skillet or wok, heat the sesame oil over medium-high heat. Add the sliced flank steak and cook for 3-4 minutes until browned. Remove the steak and set aside.
In the same skillet, add garlic and ginger and sauté for 1 minute.
Add the broccoli and cook for 5-7 minutes, stirring frequently until tender-crisp.
In a small bowl, whisk together the soy sauce, honey, and rice vinegar. Pour the sauce over the broccoli and add the beef back to the skillet. Stir to combine and heat through.
Remove from heat and stir in the cashews.
Garnish with sesame seeds if desired, and serve hot.
