This soup is very easy to make, but you have to stay all home to make it. I'm actually more of a sullungtang person, but ggorigomtang is much easier to make.
1 package ox tails
Lots of water
Salt & Pepper to taste (I always use coarse salt)
Chopped green onion
Wash the ox tails and soak them in cold water for at least an hour to remove all the blood. I prefer to boil them and then throw the water away. Either way is fine. Transfer to a big pot able to hold at least 10 cups of water. Simmer for 5-10 hours on a low heat. Skim the fat off the surface occasionally and add more water as it reduces. The longer you cook this dish the better - I always try for the full 10 hours. Serve with chopped garlic, green onion and salt and pepper to taste.