Place the macaroni, butter, garlic powder, salt, black pepper, and water in the inner pot.
Stir. Make sure nothing is stuck to the bottom of the pot and scrape the bottom of the pot well.
Secure the lid on the pot and close the pressure-release valve. Select manual/high pressure for 5 minutes.
Meanwhile, when about 2 minutes are remaining, beat the eggs and salt.
Heat oil in a nonstick 6 to 8 inch omelette pan over medium heat. Tilt the pan to spread the oil evenly. Pour in the egg mixture making sure it spreads evenly. Gently push the cooked portions of the egg so that uncooked eggs can reach the hot pan surface. Lower the heat to minimum.
Meanwhile, when cooking is complete in the instant pot, use quick release to depressurize. However, release the pressure gradually and not abruptly or else the liquid will splutter. Use a towel.
Open the lid. Select sauté, add milk, cheddar, and mozzarella cheese. Melt the cheeses by stirring for 1 to 2 minutes. The extra liquid will evaporate by the time both both the cheese melt. Press cancel.
Meanwhile, transfer the mac and cheese gently onto the top surface of thickened eggs with no visible liquid egg on it. Cook for a few minutes on low flame.
Transfer to a plate gently and serve immediately.