Wash, peel and cut the potatoes. Put the potato cubes in a saucepan filled with just enough water to cover the potatoes.
Put the lid on the saucepan and bring to a boil over high heat.
Remove the lid and boil the potatoes for 15 to 20 minutes, until easily pierced with a fork.
Add the butter skim milk, salt and pepper. Use a potato masher to smash it all together.
BETTER YET, JUST USE UP YOUR LEFTOVER MASHED POTATOES.
Add your leftover vegetables.
Return the lid to the saucepan and cook over medium-low heat until heated through.