Soak pork bones in cold water for about 30 minutes. Change the water a few times until there is little blood and the water is clear.

Place bones and ginger in a large pot. Cover with water, about 3 quarts, and bring to a boil. Simmer for about 2 hours, skimming any foam that forms on the surface.

Mix together the kochujang, dwaen jang, and sesame seeds in a small bowl. Set aside.

Remove ginger from the pot. Add a few spoonfuls of the hot broth into the paste mixture to make a thick slurry. Pour the mixture to the pot of broth and stir until there are no lumps. Add the potatoes and kaenip kimchi. Bring to a boil. Lower heat and simmer until potatoes are cooked.

Serve each bowlful with a generous topping of scallions.