Cut the rice cakes into bite-sized pieces and soak them in water while preparing other ingredients.

Slice all vegetables and beef into bite-sized pieces.

Mix soy sauce, sugar, black pepper, minced garlic, and sesame oil to create the marinade.

Marinate the beef in the prepared sauce for 10 minutes.

Heat oil in a pan and sauté sliced green onions to make scallion oil.

Add the sliced vegetables to the pan and stir-fry until slightly softened.

Add the marinated beef and stir-fry until cooked through.

Add the soaked rice cakes to the pan and stir-fry with the vegetables and beef.

Pour 1 cup of water into the pan and let it simmer until the sauce thickens and the rice cakes are tender.