Soak the beef flank in salt, vinegar and water for 15 minutes, then rinse well to remove the impurities.
In a dry pan, toast the spices over medium heat for 2 to 3 minutes until fragrant.
Heat oil in a large pot and sauté the garlic and ginger, then add the white onion, green onion and tomatoes.
Add the beef flank, toasted spices, fermented bean paste, five spice powder, Shaoxing wine, dark soy sauce, sesame oil and chicken bouillon.
Fill the pot with water, bring to a boil, then lower the heat and simmer for 90 minutes.
Once the beef is tender, take it out and set it aside. Strain out the veggies, spices and chunks to leave a clean, beefy broth.
Boil the bok choy and noodles.
Add the noodles, bok choy and beef to a bowl, ladle the hot broth over the top, and garnish.
