Thinly slice the green onions, separating the whites and greens.
Finely dice half an onion and mushrooms. Thinly slice the chili peppers (if using).
In a small container, mix together the soy sauce, sugar, mirin, oyster sauce, minced garlic, sesame oil, black pepper to taste, and a pinch of MSG (if using).
In a large mixing bowl, add the ground beef, mushrooms, and marinade. Give it a good mix until well combined.
In a wok (or pan), heat 2 tablespoons of oil over medium-high heat. Once hot, add the white parts of the green onions and the onion. Saute for 3 minutes, or until they start to go brown.
Add the beef mixture and cook for 7 to 8 minutes or until most of the liquid has evaporated. Make sure to break up the beef and keep stirring it.
Turn the heat off. Add the chili peppers (if using), green onions, and sesame oil. Give it a final mix to combine.
To serve, divide the rice into serving bowls and top with some bulgogi. Garnish with extra green onions and sesame seeds. Serve with salad greens, napa cabbage kimchi, Cucumber Kimchi, or Oi Muchim (Korean cucumber salad). Enjoy~!
