Soak the pork neck bones in cold water for an hour, changing the water once or twice.
Meanwhile, prepare the minced garlic, chopped green onion, sliced ginger, sliced onion, and washed young radish stems. Tip: Potatoes oxidize when peeled, so you can either wait to peel it until you need it, or peel and cut them and hold them in a bowl of cold water to prevent browning.
Make the seasoning paste: combine the garlic, gochujang, gochugaru, fish sauce, perilla powder, black pepper, plum syrup, water, and Knorr chicken bouillon. Set aside.
After 1 hour of soaking the pork neck bones, drain and add them to a pot with enough room temperature water to cover them. Bring it to a boil- this will take about 10-15 minutes, and once it starts boiling, only let it boil for a couple minutes. This is an asian technique for blanching meat. It gets rid of the gaminess and impurities in the pork.
Drain and rinse the pork bones thoroughly, making sure to get all the gunk out of the crevices of the bones.
Put the pork bones back in a cleaned pot. Add 8 cups of water, ginger, onion, dried shiitake mushroom, and fermented soybean paste. Bring to a boil, skim off any remaining impurities that float to the surface, then reduce the heat to medium and cover for 90 minutes. Tip: thoroughly mix the fermented soybean paste with 1/2 cup of water before adding it into the pot, so it mixes in easier.
In a separate pot, bring water a boil then blanch the young radish greens for 1-2 minutes. Set aside.
After 90 minutes, throw away the ginger and take out the shiitake mushroom to slice it.
Add 1 to 2 cups of water to the pot, then add the seasoning paste and mix well. Then add the potatoes, green onion, blanched radish greens, sliced shiitake mushrooms, and sliced serrano pepper. Cover for another 30 minutes.
After 30 minutes the potatoes should be chopstick tender. Add the sliced perilla leaves last to finish, and thats it!