In a large glass or ceramic mixing bowl, combine the soy sauce, sugar, sesame oil, sesame seeds, minced garlic, light and white parts of the green onions, sliced yellow onion, red pepper flakes, ginger, and ground black pepper. Whisk thoroughly until the sugar is dissolved and the marinade becomes smooth and aromatic.

Add the thinly sliced beef to the bowl, ensuring each piece is well-coated with the flavorful marinade. Cover tightly with plastic wrap and refrigerate for at least 1 hour to allow the flavors to fully absorb into the meat. For an even deeper flavor, marinate overnight.

When ready to cook, heat a large wok or heavy skillet over medium heat until hot. Working in batches, add the marinated beef along with a bit of the marinade. Stir-fry for about 4 to 5 minutes, allowing the sauce to caramelize slightly as it cooks. Drizzle in the honey toward the end of cooking to enhance the glaze and give the beef a touch of sweetness.

Once the meat is tender and lightly browned, transfer to a serving platter. Garnish with the dark green tops of the chopped onions and a sprinkle of extra sesame seeds if desired. Serve hot with steamed rice, lettuce wraps, or a side of kimchi for an authentic Korean experience.