Scrub the potatoes to clean and then peel them if desired. Peel and then chop the potatoes into evenly sized pieces.
Place potatoes into a large pot with cold water and place on medium heat to boil.
Once boiling, add a sprinkle of salt and keep an eye on the potatoes. Carefully drain the water from the potatoes when easily pierced with a fork - about 15 minutes.
While the potatoes are cooking, warm the milk or cream in a saucepan to a simmer, but not boiling.
Drain potatoes in a colander and then pour the potatoes back into the pot and cook off the excess water on medium heat, stirring for about 1 minute.
Mash the potatoes using a stand mixer, strainer, food mill, ricer, or potato masher. Do not over-mash.
Mix the potatoes with the butter until combined. Then add in the warmed milk and stir until smooth and creamy. Add more milk if needed. Season to taste.
Garnish with a tab of butter, chopped parsley, chives, or a sprig of fresh thyme, and serve.