Place the oxtail and beef neck bones into a large stock pot and cover with about 2 inches of water. Bring to a vigorous boil over medium-high heat and let it roll for 5 minutes. Drain and discard the water, then rinse the bones thoroughly under cold water, making sure to remove any scum, loose marrow, or coagulated blood. Clean the pot as well.

Return the washed bones to the pot and add 5 quarts (4.75 L) of fresh water. Season lightly with kosher salt. Add light and dark Thai soy sauces, both sugars, and the rest of the aromatics: cinnamon stick, Sichuan peppercorns, star anise, coriander seeds, pickled garlic, white peppercorns (whole), shallots, cilantro roots, unpeeled garlic, pandan leaves, daikon slices, and smashed galangal. Bring the mixture to a strong boil, then reduce the heat to a low simmer. Cook gently for about 3 hours, or until the meat is fork-tender and the broth is deeply infused and reduced by half.

Once the broth has developed full flavor, blend 1 cup (240 ml) of it with the fermented beancurd and fermented soybean paste using an immersion or countertop blender. Return this mixture to the main broth and stir in the ground white pepper and five-spice powder. Allow to simmer for another 10 minutes to meld the flavors.

Remove the oxtail and neck bones using tongs and place them in a large heatproof bowl to cool. Strain the broth through a fine-mesh sieve into another large bowl; you should be left with about 2 quarts (2 L) of concentrated broth. This will be more than needed for four bowls, so reserve the rest for future use. When the meat is cool, pick it from the bones, discarding fat and gristle. Moisten the meat with 1/4 cup (60 ml) of the broth and keep warm.

In a medium dry skillet, toast the green chiles over medium heat, turning them until blistered and slightly charred, about 5 minutes. Set aside in a food processor. Add garlic cloves to the pan and toast until golden and aromatic. Follow with galangal, stirring constantly until it begins to dry out.

Transfer everything into the food processor, add 1/2 cup (118 ml) of vinegar, and pulse into a smooth paste. Transfer to a bowl and whisk in the remaining 1/2 cup (118 ml) vinegar and salt. Set aside to cool.

Whisk together sugar, white vinegar, fish sauce, roasted chile vinegar, and roasted chile powder in a medium bowl until well combined and balanced in sweetness, acidity, and heat.

Bring 2 cups (475 ml) of beef broth to a boil in a small saucepan. Add the frozen beef meatballs, then reduce the heat and simmer gently, covered, for about 5 minutes or until warmed through. Keep warm.

Meanwhile, cook the rice noodles in a separate pot of boiling water according to package directions. Drain thoroughly, then transfer to a medium bowl containing the garlic oil and toss until evenly coated. Divide the noodles between four serving bowls.

In a second heatproof bowl, place 1/4 cup (60 g) of the prepared boat noodle seasoning. If using pork or beef blood, return the broth to a gentle simmer and stir it in carefully, ensuring it doesn’t coagulate by keeping the heat low. Pour this broth into the seasoning bowl, stir well, and adjust the seasoning as needed.

Divide the warm beef meatballs, reserved shredded meat, and blanched morning glory evenly among the bowls of noodles. Pour the hot seasoned broth over each bowl.

Serve with an assortment of garnishes: crispy fried garlic, extra boat noodle seasoning, ground Thai chile flakes, fish sauce, roasted chile vinegar, pork cracklings, fresh Thai basil, and a sprinkle of sugar to taste. Serve immediately while hot and aromatic.