Step 1:
Prep the meat & ingredients
Clean pork hock, remove nails, and chop into serving-sized pieces.
Rinse beef bones, brisket, and shank. Tie brisket and shank tightly with kitchen string to keep their shape during boiling.
Cut congealed blood into cubes.
Rinse all fresh herbs. Thinly slice onions and soak in ice water.
Crush lemongrass, ginger. Mince garlic, shallots, and a few stalks of lemongrass.

Step 2: Make broth
In a small pot, boil the shrimp paste with water, skim off foam, then let cool and strain to remove sediments.
In a large pot, add bones, beef shank and brisket, crushed lemongrass, 1 tbsp salt, and water (about 1 cm above the meat). Bring to a boil, skim off foam, and simmer for ~30 minutes. Remove meat and soak in cold water to firm up, then slice.
In another pot, boil pork hock with salt, ginger, lemongrass, onion, and strained shrimp paste water. Simmer until tender, then remove and slice.

Step 3: Make annatto oil
In a pan, heat oil and add annatto seeds until it turns red-orange. Remove seeds. Add minced garlic and shallots, sauté until fragrant. Set aside.

Step 4: Combine broth
In a large pot, combine all broths (beef bones, pork hock), add onions and lemongrass. Top with more water if needed.
Add the annatto oil for color. Season with chicken bouillon, salt, sugar, MSG, fish sauce, and satay chili paste. Adjust to taste.

Step 5: Serve
Blanch noodles in hot water, place in bowls. Top with pork hock, sliced beef, chả Huế, onion, and herbs.
Ladle hot broth over. Serve with lime, chili, and fresh herbs.