Place the Beef Brisket in a large pot and cover with Water; add one halved Onion, several whole Garlic cloves, sliced Ginger, the white parts of Scallions, and a tablespoon of Black Peppercorns. Bring to a boil, skim any foam, then reduce to a gentle simmer and cook until the brisket is very tender, about 1.5–2 hours.
Remove the meat and reserve the cooking liquid by straining it into another pot; discard the solids. Let the brisket cool slightly, then shred it by hand into bite-sized pieces.
While the broth is cooking or cooling, prepare the vegetables: soak or simmer the Dried Gosari (bracken) until tender, then drain and roughly chop; blanch and slice the Taro Stems if they require softening, and set aside.
Blanch the Mung Bean Sprouts in boiling water for 30–60 seconds, then drain and refresh under cold water to keep them crisp; set aside.
Cook the Dangmyeon (glass noodles) according to package instructions until soft, drain, rinse under cold water, cut into manageable lengths, and set aside.
In a large mixing bowl, combine the shredded brisket with 1–2 tablespoons Guk-Ganjang (Korean soup soy sauce), 1 tablespoon Soy Sauce, 1–2 tablespoons Gochugaru (adjust to taste), 1 teaspoon Sesame Oil, a pinch of Sea Salt, and freshly ground Black Pepper; add minced Garlic if you like an extra garlicky punch. Toss thoroughly so the meat soaks up the seasoning.
Return the strained broth to a simmer, add the seasoned shredded beef, the prepared Dried Gosari, Taro Stems, blanched Mung Bean Sprouts, and Dangmyeon. Simmer gently for 10–15 minutes so the flavors meld and the noodles absorb the broth.
Beat the Eggs lightly and slowly drizzle them into the simmering soup while stirring to create delicate egg ribbons, or simply add beaten egg and give a gentle stir to incorporate.
Taste and adjust seasoning with more Guk-Ganjang or Sea Salt if needed. Serve the soup hot, garnished with slices of the green parts of Scallions, an extra drizzle of Sesame Oil, a sprinkle of Gochugaru and a crack of Black Pepper to finish.
