Peel and cut potatoes into 2 inch cubes. Do not rinse after cutting.
Add potatoes, milk, chicken broth, and salt to a large pot. Bring to a light boil.
Reduce to a simmer and cook for about 25 minutes, stirring often, until the potatoes start to break down.
Remove from heat. Add butter, sour cream, salt, and pepper.
Whip until silky, smooth, and creamy. Taste and adjust seasoning.
