Soak the beef in a bowl of cold water until the blood is excreted (3o min- 1 hour).
Place beef in a pot and add the 12 cups of water, 6 cloves of garlic, and the whites of the green onions. Once boiling, reduce to a simmer, cover and cook 1-1.5 hours (until meat is tender). Skim off any of the foam that may have developed on top of the surface.
While the broth is simmering, place the rice cakes in a large bowl and cover with cold water. Allow to soak for 30 min then drain. You will only need to do this with frozen rice cakes usually. If you buy fresh rice cakes you can omit the soaking step.
Make the egg garnish (also known as jidan--지단), by separating the egg whites from the egg yolks into two different bowls. Lightly beat them both, then head a lightly oiled nonstick skillet over medium-low heat. Pour the egg whites into a thin layer, and tilt the skillet to thin out the eggs. Cook briefly on each side. Then repeat steps with the egg yolk.
Roll each egg into a small crepe, and slice into short thin strips. Set aside.
Clean out the skillet and place it over medium heat. Place a sheet of the gim on the skillet once it's hot and lightly toast on each side until it's nice and crispy. Stack the gim and slice into strips or cut using food scissors.
Once the beef is done cooking, strain the broth and put it back over medium heat. Cut the cooled beef into 1-1.5 inch wide strips and place into a bowl with 1 clove minced garlic, 1.5 tablespoon sesame oil, and salt and pepper to taste. Combine well and set aside.
Season the broth with the soup soy sauce and 1 tablespoon sesame oil. Add salt to taste. Once the broth starts to simmer, add rice cakes and return to a boil. Stir occasionally until softened, usually about 5-8 minutes. Remove from heat.
Serve the soup in a bowl and garnish with beef, green onions, gim strips, and egg.
