Preheat the oven to 400°F and place the beef bones, chuck roast, onion halves, and ginger on a baking sheet. Roast until they develop a nice charred, toasted surface, about 35-40 minutes. Check the onion and ginger after the 25-minute mark, as they may be ready before the bones and meat.
In a dry skillet over medium heat, toast the star anise, cloves, cinnamon stick, and coriander seeds until fragrant, about 1-2 minutes.
In a large pot, combine the roasted bones, chuck roast, charred onion and ginger, toasted spices, water, salt, and rock sugar. Bring to a boil, then reduce to a simmer and cook for 3-4 hours. Skim off any foam or impurities from the surface regularly. After one hour, remove the chuck roast. Chop it into thin slices and set it aside while you keep on cooking the beef broth.
Once the broth is ready, strain it through a fine sieve to remove solids. Add fish sauce and adjust salt as needed.Cook the flat rice noodles according to package instructions. Drain and set aside.
To serve the bowls, thinly slice the raw beef. Then, divide the cooked noodles among them. Top with sliced raw meat, slices of cooked chuck roast, green onions, and bean sprouts.
Pour steaming hot broth over the beef and toppings in each bowl. Ensure the broth is very hot to cook the raw beef and soften the onion slices. Garnish with fresh herbs and serve with lime wedges on the side.
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Notes
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