Peel the potatoes.

Cut the potatoes into 2 centimeter thick slices.

Fill a bowl with 70 degree warm water (without salt) and put the potatoes in the water. Use a thermometer, it is important that the temperature does not fluctuate more than a couple of degrees plus/minus. Let the potatoes sit in the water for 40 minutes.

Drain the water from the potatoes and rinse them in cold water.

Boil the potatoes in salted water.

Drain the water from the potatoes when they are fully tender and mash them with your preferred tool.

Add butter until the mash has a suitable consistency.

The mash can be pressed through a sieve a couple of times to make it completely smooth.

The mashed potatoes can keep for a couple of days in the refrigerator. Before serving, heat them up in a pot and add milk or cream until it has a suitable consistency.