Clean and prepare the soybean sprouts and beef.
Make the sauce by mixing soy sauce, red pepper powder, minced garlic, sesame oil, sugar, and black pepper.
Stir-fry the beef first in a pan, and when it's halfway cooked, add the soybean sprouts.
Add the sauce and stir-fry quickly over high heat.
When the soybean sprouts are wilted, add green onions and chili peppers and stir-fry once more.