Into 6 quart or 8 quart Instant Pot, add 1 cup water, potatoes and place trivet on top. Also prep double layer of foil larger than a meatloaf size. Set aside.
In a large bowl, add ground beef, eggs, breadcrumbs, garlic and onion powders, balsamic vinegar, oregano, basil, salt and pepper. Using your hands, mix just until combined (otherwise meat won’t be as tender).
Place meat mixture on prepared foil, shape into round meatloaf and fold up foil into a tight bowl. You need walls tall enough to prevent grease spilling on over potatoes during cooking. Place on a trivet.
Close the lid, set pressure release valve to Sealing and press Pressure Cook on High or Manual for 27 minutes.
After allow pressure to come down on its own for 10 minutes and then turn valve to venting to release remaining pressure.
Open the lid and make sure thermometer inserted in the middle of the meatloaf reads 160°F. Wearing oven mitts, carefully transfer meatloaf bowl onto a large plate. Then using a spatula, transfer to a cutting board or another large plate. Brush meatloaf with ketchup. Discard foil with drippings.
Remove trivet from Instant Pot, add butter, milk, salt and pepper. Mash potatoes with a masher but do not overmash.
Slice meatloaf and serve hot with mashed potatoes.