In a bowl, combine the soy sauce, sesame oil, rice vinegar, honey, minced garlic, and grated ginger.

Add the thinly sliced flank steak to the marinade. Let it sit for 10 minutes to absorb the flavors.

In a large skillet or wok, heat the vegetable oil over medium-high heat.

Remove the beef from the marinade, shaking off excess marinade, and reserve the marinade for later use.

Add the beef to the skillet in a single layer and cook for 2-3 minutes on each side, or until browned and cooked through. Avoid overcrowding the pan; cook in batches if necessary.

Remove the cooked beef from the skillet and set aside.

In the same skillet, add the reserved marinade and bring it to a simmer.

Mix the cornstarch with a small amount of water to create a slurry, then add it to the simmering marinade.

Cook for 2-3 minutes, stirring frequently, until the sauce thickens.

Return the cooked beef to the skillet, tossing to coat it evenly with the sauce.

Add the sesame seeds and chopped green onions, stirring to combine.

Season with salt and pepper to taste.

Serve the sesame beef hot over steamed rice or with a side of stir-fried vegetables.