Combine all ingredients and refrigerate for 2 hours or until ready to use.

Add pork bones and water to a large stock pot, making sure the bones are completely submerged. Bring to a simmer and let simmer for 45 minutes.

After 45 minutes, skim off the scum that has floated to the top.

Add all remaining broth ingredients except salt, and simmer for 1 more hour. While the broth is simmering, make the chili vinegar and soak the noodles (instructions below).

When the broth is done, taste and adjust seasoning with salt as needed. If it's too salty, add more water to dilute. Remember to season the broth strongly as it will be diluted by the noodles and the vegetables.

Strain the broth, and it is now ready to use. You can make the broth in advance and store in the fridge for several days. Tip: If there is a lot of meat on the bones, you can pick it off and enjoy it with your soup!

Broil the chilies and the garlic cloves in the oven until the chilies are charred and the garlic cloves are browned. You can also grill them or pan sear them.

Roughly chop the chilies and transfer to a small blender, along with the garlic, and cover with just enough white vinegar to easily blend.

Blend until there are no more big chunks, adding more vinegar if it seems too thick. If you don't have a blender, you can also pound the chilies and garlic in a mortar and pestle into a paste, then stir in vinegar.

Soak the noodles in cold water just until they are soft and pliable, 10-15 minutes for small size rice noodles ("sen lek"), 5 minutes for thin rice noodles ("sen mee").

Drain the noodles once they are soft and keep in the fridge, wrapped, until ready to use. If you let drained noodles sit uncovered they will dry out; if this happens, just soak them again briefly to rehydrate.

Bring a large pot of water to a full boil; this is for blanching noodles.

While the blanching water is coming to a boil, bring the broth (about 1 cup per person) to a simmer in a covered pot and keep hot and covered until ready to use. Do not let the broth boil uncovered as you do not want it to reduce further

Put 1 portion of noodles, bean sprouts, and spinach into a noodle strainer or sieve and blanch in the boiling water for 5 seconds. Drain and transfer to a serving bowl. (Note: I recommend blanching 1 portion at a time as it is difficult to separate noodles after they're blanched.)

Add a little garlic oil to the noodles and toss to prevent them from sticking together. Repeat with the remaining portions.

Add the meatballs to the broth and bring to a boil, then add the marinated pork and stir to cook.

Once the pork is cooked, stir in the blood (About 1 Tbsp per cup of broth), making sure you stir while adding to prevent big clumps.

Pour the broth over the noodles.

Top the soup with crispy fried garlic and cilantro. Serve with chili vinegar, Thai basil, crispy pork rind (optional), and chili flakes.