• Place the cold water, beef, onion, scallion ends, and garlic in a large pot, cover and bring to a gentle boil. Skim off the scum that forms with a spoon or ladle, and discard. Reduce the heat to a simmer. Simmer, covered, until the meat is tender enough to shred easily, about 1 ½ - 2 hours.
• Meanwhile, work on your garnishes. To make the egg garnish, separate the yolks from the whites. Whisk the yolks. Heat a lightly oiled small nonstick pan over medium low heat. Pour the yolks into a thin layer, by spreading it with a spoon. Cook each side, but do not brown the egg. Slice your omelette into thin strips. Lightly beat the whites and set aside.
• Remove the cooked meat from the broth and cool slightly. Shred the beef into thin strips and combine well with the minced garlic, sesame oil, salt, and pepper to taste. Slice the scallion diagonally into thin strips. Slice your gim (roasted dried seaweed) into thin strips, or crumble into pieces using your hands. Set everything aside.
• With a skimmer, remove the vegetables from the broth and discard. Return the broth to a boil. Stir in soup soy sauce, salt, and pepper to taste. If cooking for less than 4 people, scoop out some broth into a smaller pot to cook your rice cakes and save the rest of the broth for later. You do this because the rice cakes tend to release starches into the broth. You can always freeze any leftover broth!
• Drain the soaked rice cake slices and boil in the broth until soft, but not mushy, usually about 2-4 minutes, or until they rise to the top. Slowly stream in the egg white to form ribbons in the soup. Turn it off the heat once the egg is cooked. Ladle the hot soup into individual bowls and garnish with some of the seasoned shredded beef, egg yolk strips, sliced scallions, and gim strips.
  

TIPS: If you want to add mandu (Korean fresh or frozen dumplings), you can add them in along with the rice cake slices, stirring gently so they don’t stick to the bottom of the pot. Boil until all of them float. You can also cook the dumplings in boiling water separately, and add to the soup when the rice cakes are cooked. This will keep the soup from becoming too thick from all the starches being released into the broth.

STORING TIPS: Keep any leftover uncooked dduk in the freezer to help it last fresh longer. It's best not to have any cooked leftover dduk for the next day, so just make enough for what you will eat in one sitting.