In a large mixing bowl, combine soy sauce, Gochujang, minced garlic, brown sugar, and sesame oil. Stir well until the sugar dissolves.

Add the thinly sliced beef, tossing to coat in the marinade. Let it rest for at least 30 minutes.

Preheat a large skillet over medium-high heat. Add a splash of oil to prevent sticking.

Add the marinated beef in a single layer, cooking for 2-3 minutes on each side until charred.

While the beef cooks, mix Gochujang, soy sauce, sesame oil, and water in a small bowl until smooth for the dipping sauce.

Remove beef from skillet and let it rest. Serve with dipping sauce on the side, garnished with sesame seeds and green onions.