Cut the beef brisket and vegetables into bite-sized pieces.
Add the beef brisket to a pan and stir-fry over medium heat.
When the meat is about halfway cooked, add onion, green onion, shiitake mushrooms, and enoki mushrooms, and stir-fry together.
Pour in the sauce made by mixing soy sauce, mirin, sugar, and water.
Add tofu and dangmyeon (glass noodles), then bring to a boil.
Once all ingredients are cooked, turn off the heat.