Soak the miyeok
Rinse the dried miyeok a couple of times in cool water to remove any grit, then soak it in a bowl of cool water for 10 minutes until it softens and unfurls. Drain it well, squeeze out the excess water, and tear it into bite-size lengths so it cooks evenly.
Sauté the beef
Set a pot over medium heat and warm 1 tbsp of toasted sesame oil until it shimmers. Add the beef and garlic, then stir-fry for 3 minutes, breaking up the slices, until the beef is mostly browned. Add the drained miyeok and 1.5 tbsp of Korean soup soy sauce, and keep tossing for 1 minute until everything is glossy and fragrant.
Simmer the soup
Pour in all 1.5 l of water and scrape up any browned bits from the bottom of the pot. Bring the soup to a boil, then lower the heat and simmer for 15 minutes until the broth tastes rich and the miyeok is silky.
Season and serve
Taste the soup and stir in 1 teaspoon of salt a little at a time, stopping early if the broth already tastes seasoned enough. Finish with a pinch of black pepper if you like, then ladle the miyeok guk into bowls and serve it hot.
