1. Soak beef short ribs in cold water for 2 hours to get rid of any blood.
2. Strain beef, add it to a pot, and cover with water. Bring to a boil and cook for 5 minutes to get rid of any scum.
3. Strain the beef and rinse under cold water.
4. Add back the beef to a pot with radish, onion, white portion of scallions, ginger, garlic, black peppercorns, and mirin. Cover with water and simmer on low for 3-4 hours.
5. Half way through, remove the radish and slice it into bite-sized pieces.
6. Discard the aromatics and set aside the beef.
7. Strain the broth and season with soup soy sauce, fish sauce, and salt.
8. Soak sweet potato noodles in warm water for 10 minutes.
9. Add soaked noodles to a pot along with the sliced radish, beef, and some broth. Bring to a boil and cook for 3-5 minutes.
10. Serve with scallions, course salt, pepper, radish kimchi, and rice.
