When the potatoes are soft and falling apart, drain the water, being sure to reserve at least 1 cup incase you need it.
Allow the potatoes to cool enough that you can handle them.
Once cooled, use a dull-edged knife to peel the skins. You can leave them on if you prefer skins in your mashed potatoes.
Mash the potatoes, butter and whipping cream together. Test the consistency. If you like it, you only have salt left to add. If you don't like it, add more cream or some potato water (as you wish) until you reach your desired consistency.
Serve with.... BUTTER!
Please note that the nutrition data below is a ballpark figure. Exact data is not possible.