Make marinade by combining the garlic, green onion, soy sauce, sugar, water, sesame oil, sesame seeds, and ground black pepper in a large bowl. Mix it well with a spoon until the sugar is well dissolved.
Add the sliced beef and mix everything by hand until the beef is covered in the marinade. Keep in the fridge at least 30 minutes.
Cook on a pan or a grill, and transfer to a plate or a cast iron plate to serve with rice, lettuce, ssamjang, and more side dishes.
To eat, wrap a spoonful of rice, a piece of bulgogi, and a little bit of ssamjang in a lettuce leaf. Fold it over and eat. Repeat!
