Clean the crabs and boil them until cooked. Remove the meat from the shells and set aside the crab roe separately.

Blanch the pork bones, rinse them, then add them to the pot with the crab boiling water. Simmer until tender. Add salt, sugar, and a little MSG. Skim off any foam to keep the broth clear. Add 2 onions to the pot while simmering for a sweeter, more fragrant broth. Once done, remove and discard the onions.

Finely chop the shallots and sauté them until fragrant. Add the crab roe and annatto oil, stir-fry until the mixture turns a nice color, then add it to the finished broth.

In the same pan, stir-fry the crab meat with a little seasoning powder and pepper.

Taste and adjust the broth as needed, adding a piece of rock sugar. Add the bánh canh noodles. Mix a little tapioca starch with water and pour it in, stirring well to prevent lumps. When the broth thickens slightly, it's ready.