Wash the pork bones and let them dry. Soak the dried wood ear mushrooms in water to soften them. Rinse the dried shrimp and allow them to dry. Mince the saw leaves, cilantro, and scallions, keeping the roots of the cilantro and scallions. Next, mince the betel leaves and wood ear mushrooms. Thinly slice the shallots. Cut the tomatoes into quarters. Put the minced crab into a small pot. Gradually pour water into the pot and stir the crab with your hands. Pour the crab through a sieve into a larger pot to filter out tiny bits of crab shells. Repeat this step a couple of times. Add the minced wood ear mushrooms and betel leaves to the ground pork. Season the mixture with pepper, soup powder, and brown sugar. Mix well and let the meat rest for 10 minutes.
Blanch the pork ribs with salt and scallions for 2 to 3 minutes. Transfer the bones to a cold water bath and clean them.
Next, add water to a pot together with 1 shallot and the roots of cilantro and scallions. Simmer for 30 to 45 minutes over medium heat.
Set the filtered crab pot on the stovetop and season it with salt. Bring the mixture to a boil over medium heat. Use a chopstick to lightly stir the crab to keep it from sticking to the bottom of the pot. Once boiled, set the heat to low. After 3 to 5 minutes of cooking over low heat, transfer the crab meat that floats on the surface to a bowl and turn off the stove. Spread a betel leaf on a chopping board on its glossy side. Place some ground pork on the leaf's surface and roll it up carefully. Use the petiole to lock the roll. Repeat this step for the remaining leaves and pork. Pour some olive oil into a heated pan and fry the fish cakes until they turn golden brown on all sides. Put them onto paper towels to absorb the oil. Add the betel leaf rolls into the same pan and fry them for 5 to 10 minutes. Transfer them to another paper towel-lined plate. Add the pork fat into a pan and stir for 10 to 15 minutes over medium heat. Set aside.
In the same pan, add the sliced shallots and stir until they turn light yellow.
Add the tomatoes to the same pan and stir lightly. Then, add the dried shrimp and continue stirring for 2 to 3 minutes. Pour the tomatoes and shrimp mixture into the pot that you used to cook the crab and simmer it over low heat. Next, pour cashew oil into a heated pan and stir in the crab mustard. Stir lightly for 3 to 5 minutes on low heat. Add the crab mustard to the crab broth pot and simmer over low heat. Season the broth with fish sauce, soup powder, and brown sugar. Pour in the pork broth and keep on simmering over low heat to keep the stock heated.
Blanch the water spinach briefly and transfer it to a cold bath. Rinse the noodles about 10 minutes in advance. Then, blanch them in boiled water for 30 seconds.
Arrange the noodle soup and enjoy it with fresh vegetables on the side.