Place peeled and cubed potatoes in a large pot. Cover with water and allow to cook on medium/high until it reaches a boil. Reduce heat (medium) and cook until potatoes are tender.
Drain water, turn off heat, and return to pot. Add butter and milk and start mashing.
Next add sour cream, salt, pepper, and 1 cup shredded cheese. Continue to mash or use a hand mixer to get a really creamy texture.