Next, add 1 cup cold water to the Instant Pot pan and insert the trivet into the pot. Prepare the casserole by whisking the eggs, milk, salt, and pepper together until combined. Then lightly grease a 6x4 oven-safe baking dish. Place the defrosted hash browns in the bottom of the dish, then sprinkle the sausage over the top. Last, pour the egg mixture into the casserole dish and sprinkle with the cheese and cover with foil. Then place the casserole dish on the trivet, close the lid, and make sure the valve is set to "seal."