Bring a large pot of water to boil; carefully place oxtails in water and boil 15 minutes. Remove from heat and rinse to remove scum.
Return oxtail to clean pot and cover with water. Add carrots, daikon, ginger, onion and burdock. Cook for 2 hours or until meat is very tender. Season to taste with salt. Stir in minced garlic.
In a small bowl, mix together soy sauce, sesame oil, red pepper flakes and black pepper.
If using somen noodles, cook according to directions on package; drain; rinse with cool water and portion among serving bowls. Divide oxtails and vegetables among serving bowls. Drizzle some dipping sauce on top and sprinkle with scallions and sesame seeds. Serve any extra dipping sauce on the side.
Dipping sauce adapted from Dok Suni by Jenny Kwak.