Pour 1 cup of water into pressure cooker. Add steamer basket and fill with potatoes. Cook at high pressure for 8 minutes, then quick-release the pressure.
Meanwhile, add butter, milk, salt, pepper, garlic powder, and onion powder to a small sauce pan. Bring to a simmer and mix well. Keep warm until potatoes are ready.
Add potatoes to a large mixing bowl and pour in milk/butter mixture. Using a potato masher, mash and mix potatoes until desired consistency is reached.