1.In a shallow pan, bring 6 cups of water to a boil. Add the pork ribs and bring the water back up to a simmer. Once simmering let it cook for an additional 2 minutes then turn off the heat.
2.Drain and wash the ribs clean under cold running water. Place ribs into the insert of an instant pot. Add ginger slices and 8 cups of water into the pot. Toggle the knob to sealing and set the instant pot to manual on the high pressure setting for 30 minutes.
3.In the meantime, prepare the watercress by washing thoroughly in water. After the instant pot is done, do a quick release of the pressure. Take the lid off then stir in 1ΒΌ teaspoon of salt and cover. Toggle the knob to sealing and set the instant pot to manual on the high pressure setting for 10 minutes.
4.After the instant pot is done, do a quick release of the pressure. Take off the lid and give your soup a quick stir, then use a fine-mesh strainer to remove any floating particles. Next, use a ladle to skim off the excess grease that is floating at the top of the soup.
5.Press the saute button on high then stir in the watercress and wait for it to simmer. Then turn off the saute and press it again on low and cook the soup for 15-30 minutes.
6.Add 1 teaspoon of salt and white pepper to soup then mix well. Serve the soup with a hot bowl of rice and a small dish of soy sauce as a dipping sauce for the pork.