Cut the napa cabbage and beef brisket into bite-sized pieces.
Layer cabbage at the bottom of a pot and place beef brisket on top.
Slice onion, green onion, and spicy chili peppers, then place them over the beef.
Pour in soy sauce, minced garlic, sugar, black pepper, and rice rinsing water (or water).
Cover with a lid and steam over medium heat for 10–15 minutes.
Once the cabbage is tender and the beef brisket is soft, it's ready to serve.