Crush and finely mince the garlic cloves.

Finely chop the green onions.

Place the minced garlic and chopped green onions into a large mixing bowl.

Add soy sauce and sugar to the bowl.

Add water, sesame oil, and ground black pepper.

Add toasted sesame seeds, crushing them between your fingers to release their aroma.

Mix the marinade well with a spoon until the sugar is completely dissolved.

Thinly slice the beef tenderloin. It's easier to slice if the beef is partially frozen for about 1.5 hours.

Add the sliced beef to the bowl of marinade.

Use your hands to gently mix the beef and marinade together, ensuring all pieces are well-coated.

Cover the bowl and let it marinate in the refrigerator for 30 minutes.

Spread the marinated beef in an even layer over a grill basket.

Place the grill basket over a portable gas stove or grill set to medium heat.

Cook for about 3-4 minutes, frequently flipping the grill basket and using tongs to move the meat around for even cooking.

Once the beef is fully cooked and slightly browned, it's ready.

Serve the hot bulgogi immediately with lettuce, rice, and side dishes.