Bring a large stock pot of water to a rolling boil.
Wash and cube all potatoes. If you don't like potato skins, peel that off.
Once the water is boiling, pour the potatoes in and boil for 15 minutes or until soft.
Remove from heat and drain.
In a large bowl, add the potatoes to the butter, salt, and pepper.
Add in the milk and blend slowly with a hand mixer.
Increase the hand mixer speed slowly until the potatoes are creamy.
Add in your preferred amount of sour cream and blend again.
Top mashed potatoes with green onions or cheddar cheese.
Serve immediately while still warm.