Prepare the broccoli: Wash and cut the broccoli into small, bite sized florets. If the stems are thick, peel them and slice them thin so they cook evenly.
Brown the beef: Heat the olive oil in a large skillet or wok over medium high heat.
Add the ground beef and cook, breaking it apart with a spoon, until it is fully browned and no longer pink. This takes about 5 to 6 minutes. Drain any excess fat if needed.
Cook the broccoli: Add the broccoli florets to the pan with the cooked beef.
Stir fry for 2 to 3 minutes until the broccoli turns bright green and starts to get tender but still has a little crunch.
Add the garlic: Push the beef and broccoli to one side of the pan. Add the minced garlic to the empty space and cook for 30 seconds until fragrant. Stir everything together.
Make the sauce: In a small bowl, whisk together the soy sauce, honey, rice vinegar, and sesame oil.
Pour the sauce over the beef and broccoli and stir to coat everything evenly.
Thicken the sauce: Give the cornstarch slurry a quick stir, then pour it into the pan. Stir constantly for 1 to 2 minutes as the sauce thickens and becomes glossy.
Finish and serve: Taste and adjust seasoning with salt, pepper, and red pepper flakes if using. Remove from heat, garnish with green onions and sesame seeds, and serve immediately over rice or your favorite base.