Turn on the sauté function of the Instant Pot and add the coconut oil or your fat of choice when the metal insert is hot.
Toss in the shallots and shiitake mushrooms, and cook until the shallots are softened and the mushrooms are cooked, about 3 to 5 minutes.
Stir in the ginger and garlic and cook until fragrant. Add the pork cubes and stir well.
Pour in the coconut water and the fish sauce. (I normally use ¼ cup fish sauce, but if you’re new to fish sauce, start with 3 tablespoons.) Stir well, scraping any browned bits from the bottom of the Instant Pot.
Cancel the sauté function. Lock the lid of the Instant Pot and program it to cook for 40 minutes under high pressure.
When the stew is finished cooking, allow the pressure to drop naturally. If you’re impatient, wait 15 minutes and then manually release the pressure.
Check that the pork pieces are fork tender. (If it’s still a little tough, cook under high pressure for another 5 to 10 minutes.) Taste and adjust the seasoning of the sauce with more fish sauce or salt if needed. Use a slotted spoon to transfer the pork to a serving platter. Cover to keep warm.
Carefully add the cut carrots to the cooking liquid (watch out for hot splashing liquid!) and cook for 2 minutes under high pressure.
Release pressure manually and remove the lid when the contents have depressurized.
Spoon the carrots and cooking liquid onto the pork and garnish the stew with sliced scallion or cilantro.