In a mixing bowl, combine soy sauce, brown sugar, sesame oil, garlic, ginger, green onion, and black pepper. Add the sliced beef and mix well. Let it marinate for at least 30 minutes.

Preheat the grill or pan over medium-high heat. Cook the marinated beef for about 5-7 minutes, or until fully cooked, stirring occasionally.

In a bowl, place a serving of cooked rice. Top with cooked beef, carrots, cucumber, and spinach. Garnish with sesame seeds and a fried egg if desired.