Gather all ingredients and equipment.
In a bowl, mix soy sauce, brown sugar, sesame oil, garlic, ginger, and black pepper.
Add the sliced beef to the marinade and let it sit for at least 30 minutes.
Heat a skillet over medium-high heat.
Add the marinated beef to the skillet, reserving the marinade.
Cook the beef for about 5 minutes until browned.
Pour the reserved marinade into the skillet.
Simmer for 2-3 minutes, allowing the sauce to thicken.
Garnish with sesame seeds and chopped green onions.
Serve hot over rice or noodles.