Place all ingredients in a large Ziplock bag and use the water displacement method to remove air and seal. Then it's into the water bath for 45 to 60 minutes. Carefully do a quick squeeze test to confirm potatoes are soft and cooked through.
Transfer the potatoes and liquid to a bowl and mash.
OR for pureed potatoes with no lumps: Drain the liquid into a warm bowl, then pass the cooked potatoes through a potato ricer or food mill in with the liquid. Stir to combine.
Taste for seasoning and serve warm.
Add a few heavy spoons to the bag if it is not staying submerged in the water.
The recipe can easily be scaled up or down depending on how much you need.
Serve with chopped fresh herbs such as chives.
Optional: Add some fresh thyme sprigs and some of the potato peels to the bag to infuse more potato thyme flavors.