Place potatoes in a colander and rinse under cold water for 1 minute. Drain.
Fill a Dutch oven with 1 inch of water and place a steamer basket inside. Add potatoes to steamer basket, place Dutch oven over high heat with lid on top until water comes to a boil. Once water comes to a boil, reduce heat to medium and cook 20 to 25 minutes, until potatoes are fork tender.
While potatoes are cooking, place milk, butter, salt, and pepper in a medium saucepan and heat over medium-low until butter is melted. Keep warm.
Drain potatoes and return to Dutch oven. Place over low heat to evaporate any water.
Place potatoes in the bowl of an electric mixer and using a whisk attachment, turn mixer on LOW for 30 seconds to break up potatoes.
With mixer on LOW, slowly add milk mixture.
Once milk mixture has been added, turn mixer to HIGH for about 2 minutes, until no lumps remain. Serve.