Add the red potatoes to the steamer insert of an instant pot. Pour in one cup of water.
Pressure cook the potatoes in high for 12 minutes.
Use quick pressure release to remove the lid.
Add the potatoes to a large bowl with the butter (the hot potatoes will melt the butter) or drain the Instant Pot cooking pot and put the potatoes back with the butter.
Use a potato masher to mash the potatoes.
Optional: add milk for smoother consistency.
Stir in seasonings, milk (if you wish) and spices and enjoy!