- In separate bowls, soak the beef bones and beef brisket in cold water for about 1 hr to draw out as much blood from the bones as possible. Rinse well and drain. Keep beef brisket in the refrigerator until ready to use.
- Place all the bones in a large stockpot and fill with cold water until the bones are fully covered. Bring water to boil on high heat then reduce to medium heat and boil for further 5 mins. Drain and rinse the bones and the stockpot to remove the scum.
- Again, fill the stockpot with cold water, enough to submerge the bones in about 2-3cm. Bring to boil over high heat then reduce to medium heat. Cover and let it continue boiling for 5 hrs or longer. Check the pot periodically and add water (boiling hot water to maintain cooking temperature) to ensure bones are fully submerged underwater throughout.
- Then, add the beef brisket into the soup and continue to cook for 1 to 1½ hrs. Once cooked, remove, cool and slice thinly.
- Remove soup from heat. Skim away any fats floating with a spoon or if the soup will be used later, refrigerate overnight and spoon away excess fat when solidified.
- To serve, cook somen separately in a pot of water. Drain and place in a bowl then pour the hot soup over. Garnish with sliced beef and chopped spring onions. Alternatively, enjoy seolleongtang with rice.