Whisk together the soy sauce, brown sugar, honey, sesame oil, garlic, ginger, grated onion, grated Asian pear, rice vinegar or mirin, and black pepper in a large bowl.
Add the thinly sliced beef, sliced onion, and green onions, then mix until the beef is evenly coated in the marinade.
Cover the bowl and marinate the beef in the refrigerator for at least 30 minutes or up to overnight.
Heat a large skillet with the neutral oil over medium-high heat.
Add the marinated beef in a single layer, working in batches if necessary to avoid overcrowding the pan.
Cook for 2 to 4 minutes, stirring occasionally, until the beef is fully cooked and lightly caramelized around the edges.
Garnish with sesame seeds and additional green onions.
Serve warm over rice, in lettuce wraps, or with your favorite vegetables and side dishes.