Wash and scrub your potatoes for unpeeled, or wash and peel, totally your preference. Quarter the potatoes.
Add the water to your pressure cooker, insert the steamer tray or basket, add the potatoes and garlic to the tray or basket.
Place the lid on and lock, add the weight (the jiggler), turn on the heat to high. when the jiggler starts to move and vent pressure, indication full pressure, start your timer for 6 minutes and reduce the heat to low or medium low to maintain full pressure.
When 6 minutes have passed, turn off the heat and move the pressure cooker to an unused burner to cool and release the pressure naturally, about 10-15 minutes.
When the pressure is fully released, open the lid.
Transfer the potatoes to a medium sized pot (you can use a sturdy mixing bowl but I feel that a pot is much easier to work with) and using a potato masher, mash up the potatoes. Add a splash of milk and 2-4 tablespoons of butter and mash that in.
Serve as side dish.