First, boil the bones briefly in a pot of water for 5 minutes, then drain and rinse. This removes impurities and ensures a clearer broth.
Simply grill or fry the onion and ginger halves until they are slightly burned. Trust me this would add a smoky flavor.
Now place the blanched bones, charred onion and ginger, spices, fish sauce, brown sugar, and water in a large stockpot. Bring to a boil, then reduce heat and simmer for at least 1 hour.
As the broth simmers, use a spoon to remove any fat that accumulates on the surface. This will result in a clear broth.
Now after six hours strain the broth through a fine-mesh sieve into a clean pot. Discard the solids.
You can adjust the taste and seasoning with additional fish sauce or salt if needed.
Prepare noodles and toppings:
Soak the rice noodles in warm water for 30 minutes. Drain and set aside.
Freeze the beef for 30 minutes. Now cut this beef into thin slices. Freezing the beef makes it easier to achieve thin, even slices.
Thinly slice the onion. Wash the bean sprouts and herbs, and cut lime wedges.
Assemble and serve:
Bring the broth to a simmer.
Divide the softened rice noodles into serving bowls.
Add the sliced beef to the bowls.
Pour the hot broth over the noodles and beef.
Briefly blanch the beef in the hot broth. This ensures the beef is cooked through while remaining tender.
Top with sliced onions, bean sprouts, basil, and cilantro.
Serve with lime wedges, chili sauce, and hoisin sauce on the side.