Boil 2 cups of water. Place dried shiitake mushrooms in a large bowl and pour boiling water over it. Let it soak for 45 minutes.
Once mushrooms are done soaking, make the congee. Rinse the rice in a fine mesh strainer for 30 seconds. Add the rinsed rice to the Instant Pot. Add the soaked mushrooms along with the soaking liquid to the pot. Add the remaining 2 cups of water. Add the vegetable broth, ginger, and salt. Stir and place the lid on, making sure the lid is secure and the knob is on sealing. Cook on manual high pressure for 30 minutes.
Once the timer goes off, let it naturally release. Stir congee and loosely place the lid back on. Let it sit for 15 minutes to thicken. If it’s too thick, feel free to add a little bit of water. Remove the large ginger chunks. You can remove the mushrooms and cut them into smaller pieces and stir them back into the congee. Serve with your favorite optional toppings. I did soy sauce, tofu, sautéed shiitake mushrooms, tofu, furikake, chili oil, and pickled radish.
*To make on the stovetop, after step 2 of adding all the ingredients, simmer on the stove on low heat covered for 1 hour. Stir occasionally. After an hour, turn heat off, stir, partially cover, and let it sit for 20 minutes to thicken. Remove ginger pieces and enjoy!