Add all ingredients except shiitake to the pressure cooker bowl and stir. Place shiitake mushrooms on top.
Close the lid, seal the pressure valve and set the pressure cooker to cook on high for 45 minutes. Use the same amount of time whether using a Multicooker/Instant Pot or stovetop pressure cooker.
After the time has finished, release the pressure and stir. If you prefer to have some of the shiitake mushrooms sliced on top of the congee, set some aside for this. Add additional water if a thinner soup is preferred.
Adjust the salt if desired and serve with your chosen toppings.
Store in the fridge for 3 days or in the freezer for 1 month. Reheat on the stove with a little extra hot water added or in the microwave.