Add the potatoes, garlic, water, and salt to the pot.
Secure the lid, close the pressure valve, and cook for 16 minutes at high pressure.
Quick-release pressure.
Add the butter, mash, then slowly add milk and heavy cream if using while mashing the potatoes.
Optional: add the parmesan or any other ingredients if desired.
Top with freshly ground black pepper and chives. Add more butter if desired.