Slice onion and green onion into thin strips.
Heat oil in a pan and sauté the onion and green onion.
Add beef brisket and stir-fry quickly over high heat.
Season with soy sauce, sugar, minced garlic, and black pepper.
Place the stir-fried beef brisket on top of rice.
Finish by topping with egg yolk, chopped scallions, and seaweed flakes.