Trim off any thick layer of surface fat. In the pot, rinse the ribs with cold water a couple of times to remove surface blood and bone dust. Drain, and fill the pot with enough water to cover the ribs, about 4 cups.
Close the lid tightly. Press the “Manual” function and High Pressure, and using the “-” button. Make sure the pressure switch is turned to “sealing”. When finished, carefully release the pressure.
Return the ribs to the pot, and add the onion, garlic, ginger and soup soy sauce. Add water. Pressure cook the ribs, depending on the thickness of the meat. NPR 10 minutes.
Put the ribs back in the pot along with the cut radish. Change the Instant Post setting to “Saute”, and boil until the radish turns translucent. Add the optional noodles before turning the Instant Pot off.
Salt and pepper to taste. Skim off or use a fat separator to remove any remaining fat, if serving while still hot. Or chill the soup and discard solidified fat. Garnish with the chopped scallions to serve.