In a bowl, whisk together soy sauce, brown sugar, mirin, sesame oil, minced garlic, grated ginger, and grated pear (if using).
Place the thinly sliced beef in a shallow dish or a resealable plastic bag. Pour the marinade over the beef, ensuring each slice is well coated. Marinate in the refrigerator for at least 2-3 hours, or overnight for maximum flavor.
Preheat the grill to medium-high heat.
Remove the marinated beef from the refrigerator and let it come to room temperature for about 15-20 minutes.
Grill the beef slices for 2-3 minutes per side, or until cooked to your desired level of doneness.
Sprinkle the grilled beef with sesame seeds and sliced green onions.
Serve the Korean BBQ Beef Bulgogi with fresh lettuce leaves for wrapping and steamed rice on the side.
