Put the pork bones in a large pot, cover with cold water, and bring to a hard boil for 5 minutes. Drain and rinse the bones and the pot under running water, scrubbing off any grey scum stuck to the bone. Skip this and the broth turns cloudy and smells distinctly of pig.
Return the rinsed bones to the pot with 1.5 liters / 6 cups fresh water. Bring to a boil, then simmer, partly covered, for 60 minutes, skimming any foam that rises in the first 15 minutes.
Stir in the gochugaru, gochujang, doenjang, garlic, and ginger. Simmer 10 more minutes so the paste dissolves into the broth instead of sitting on top.
Add the anchovy-kelp broth and the potatoes. Simmer 15 minutes, until a knife slides into the potato with only slight resistance.
Add the napa cabbage leaves and perilla seed powder. Simmer 8 minutes, until the cabbage has gone fully soft.
Stir in the perilla leaves and scallions, season with salt to taste, and simmer 2 more minutes.
Serve directly from the pot. If anyone wants ramyeon noodles added to the leftover broth once the meat is gone, drop them in at a rolling boil for 3 minutes.