Creating Korean Beef is straightforward if you follow these simple steps:

1. Prepare the Marinade: In a bowl, mix soy sauce, brown sugar, sesame oil, minced garlic, grated ginger, and black pepper.
2. Marinate the Beef: Add the thinly sliced beef to the marinade. Let it sit for at least 15 minutes to absorb the flavors.
3. Heat the Pan: In a large skillet or wok, heat the vegetable oil over medium-high heat.
4. Cook the Beef: Add the marinated beef to the pan in a single layer. Sear for about 2-3 minutes until browned, stirring occasionally.
5. Add Vegetables: Toss in the broccoli and bell peppers. Stir-fry for another 3-5 minutes until the vegetables are tender yet crisp.
6. Finish Cooking: Ensure the beef is cooked through and the vegetables are vibrant and tender. Remove from heat.
7. Garnish: Sprinkle chopped green onions and sesame seeds over the dish.
8. Serve: Serve the Korean Beef hot over a bed of cooked rice.

These steps will guide you in creating this incredible dish effortlessly.