Wash, peel and quarter the potatoes, trying to keep the potato pieces roughly the same size if possible.
Rinse peeled potato quarters in cold water to remove excess starch. If you need to go work on another part of your meal, you can leave your potato quarters covered in cold water in a pot for a number of hours, just drain and re-fill with cold water when the water warms as needed.
When ready to prepare, drain and fill pot once more with cold water (until potato quarters are just covered). Turn your burner on high and when water starts to boil, back the heat down until the water is rapidly simmering. Simmer for 15-20 minutes or until a fork easily spears through your potatoes.
Drain potatoes in a strainer and return to pot. Take off the burner and mash with a potato masher. When mostly mashed, pour in the melted butter and mix with an electric mixer. Gradually mix in the warmed milk until you reach your desired consistency. Salt and pepper to taste.