Preheat the oven to 350F.
Thinly slice the mushrooms and mix well with soy sauce, oil, garlic powder and black pepper. Spread them in a single layer on a baking tray and bake for 50-60 minutes or to your liking.
While the mushrooms are being baked, cook the congee. Start by mixing the ground pork with 1/2 teaspoon of salt. Set aside.
Rinse rice under water, drain and set aside.
Turn on the Instant Pot with Sauté mode. Once it's hot, add a little bit of oil and then add ginger and shallots, stir and cook for 30 seconds or until fragrant. Add pork, stir, break up the pork and cook until the outside is no longer pink. Add rice, cook for 30 seconds to a minute, then add water and 1/2 teaspoon of salt.
Put the lid of the Instant Pot on, set the van to Seal and choose Porridge mode, High pressure and cook for 10 minutes.
After the high pressure cooking is over, let the Instant Pot releases pressure naturally (this may take around 15 minutes). Then carefully open the Instant Pot, gently stir, taste the congee and check for its consistency. If it's too thin, you can turn on the Sauté mode to reduce the liquid. If it's too thick, add some boiling water to thin it out. Season the congee to your liking.
At this time, the mushrooms should be ready. Add congee to serving bowls, top with mushrooms, scallions, plenty of black pepper and other toppings and serve hot.