01 - In a large soup pot, combine chicken stock, pork bones, onion halves, smashed garlic, salt, and sugar. Bring to a rolling boil over high heat, then reduce to medium-low heat and let simmer for 30 minutes. Skim off any foam or impurities that rise to the surface for a clearer broth.
02 - Add fish sauce to the broth and stir to incorporate. Using a slotted spoon or strainer, remove and discard the pork bones and onion halves. The broth should now be flavorful and clear.
03 - Add peeled and deveined shrimp to the simmering broth. Cook for 2–3 minutes until just pink and opaque. Remove shrimp immediately with a slotted spoon and set aside on a plate to prevent overcooking.
04 - Gently add crab meat and sliced fish cakes to the broth. Simmer on low heat for 5–7 minutes to allow the seafood flavors to meld with the broth. Avoid vigorous boiling to keep crab meat intact.
05 - While broth simmers, cook banh canh noodles according to package directions (typically 3–5 minutes in boiling water). Drain thoroughly and rinse lightly with cool water to prevent sticking. Set aside.
06 - Divide cooked noodles evenly among 4 serving bowls. Arrange cooked shrimp, crab meat, and fish cakes on top of the noodles in an appealing presentation.
07 - Ladle hot broth generously over each bowl, covering the noodles and seafood. Top with sliced spring onions, fried shallots, chopped cilantro, and fresh black pepper. Serve with lime wedges and sliced chili on the side for individual seasoning. Serve immediately while piping hot.