Put the beef in a pot and add enough cold water to fully cover the meat. Bring it to a boil and skim off any scum that rises to the surface. Once impurities stop appearing, remove the beef and set it aside.
Fry the aromatics
Heat oil in a clean pot, preferably a heavy, thick-walled one such as a Dutch oven (casserole pot). Add sliced onion, garlic cloves, ginger slices, bay leaves, star anise, Chinese cinnamon, and Sichuan pepper. Fry until the onion softens and browns on the edge.
Stir in Sichuan chili bean paste and fry for 20 seconds or so, then add Shaoxing rice wine, light soy sauce, dark soy sauce, sugar, chopped tomatoes, and 6 cups (1½ litre) of hot water. If using a thin-walled pot with a loosely fitted lid, increase the water by ½-1 cup
Cook the beef
Return the blanched beef pieces to the pot. Once the liquid starts to simmer, cover with a lid and reduce the heat to low. Leave to simmer for 1 hour 30 minutes, or until the beef becomes so tender that it breaks apart easily (see note 4 for Instant Pot method).
Transfer the beef to a plate. Strain the broth through a large sieve, discarding the solids and keep the clear soup.
Fry the topping
While the beef is cooking, prepare the topping. Sizzle minced garlic and ginger in oil, then add chopped pickled mustard greens and fry until fragrant. Set aside.
Boil the noodles
Bring a pot of water to a rolling boil. Add the noodles of your choice and cook until just done. Add the bok choy and blanch for 10 seconds.
Assemble the bowls
Divide the noodles in serving bowls, then add bok choy and beef chunks. Ladle in the hot broth. Top with the fried pickled vegetables and cilantro if using.
Store leftovers
Store any leftover beef and broth in airtight containers in the fridge for up to 3 days or in the freezer for up to 3 months. Keep the fried pickled vegetables in a separate container under the same conditions. Defrost and reheat each component gently before serving.
Video
Notes
1. Other beef cut options include brisket, chuck, and short ribs.2. Pickled mustard green (aka Chinese sour vegetable, Suan Cai/酸菜) can be replaced by other types of pickled/preserved vegetables, such as Ya Cai (芽菜), Zha Cai (榨菜).3. For an average appetite, a good portion of noodles is about 5 oz (140g) of fresh noodles or 3 oz (85g) of dried noodles.4. Instant Pot Method: Blanch the beef as usual. Use the sauté function to fry aromatics and spices, then add the beef and broth ingredients. Cook on high pressure for 25 minutes (add 5 more for thick pieces) and let the pressure release naturally.