Coat the bottom and sides of the steaming basket lightly with cooking spray or oil.
Beat the eggs in a large bowl. Add the ground meat, onions, parsley, oats, catsup, salt, garlic, and pepper. Mix with your
hands until blended. (The mixture may be fairly moist.)
Transfer to the steaming basket and press into a disc of uniform thickness. (If your steaming basket has a central lifting pole, either remove it or shape the loaf around it.) Spread a very thin coating of chili sauce on top.
Pour 2 cups of water into a 6-quart or larger cooker. Place the potatoes in the water. Set the steaming basket with the meatloaf on top of the potatoes. Wrap the carrots tightly in foil and set them on top of the meatloaf.
Lock the lid in place. Over high heat bring to high pressure. Reduce the heat just enough to maintain high pressure and cook for 15 minutes. Turn off the heat. Quick-release the pressure. Remove the lid, tilting it away from you to allow steam to escape.
Use tongs to lift the foil-wrapped carrots. Check the meatloaf for doneness: an instant-read thermometer inserted into the center should read at least 155 degrees. If the meatloaf requires more cooking, nestle (but do not lock) the lid in place and steam over high heat for another few minutes.
Lift the meatloaf basket from the cooker and let rest in the basket for at least 5 minutes before slicing, if you like place in a preheated oven to slightly brown the top. Meanwhile, prepare the potatoes: Drain the potatoes and return them to the empty cooker. Set over very low heat. Add the butter and mayo. Use a masher to smash the potatoes. For a moister mixture, stir in additional milk. Add salt and pepper to taste. Unwrap and slice the carrots, add salt to taste.