In a mixing bowl, combine soy sauce, brown sugar, sesame oil, garlic, ginger, gochujang, scallions, and black pepper. Add the sliced beef and mix well. Marinate for at least 30 minutes.

Heat a skillet over medium-high heat. Add the marinated beef and cook for about 5-7 minutes, or until the beef is cooked through and caramelized.

In serving bowls, place a cup of cooked rice. Top with cooked beef and mixed vegetables. Garnish with sesame seeds and a fried egg if desired.