Boil whole blue potatoes in a large saucepan with abundant salted water until they become fork tender

In a smaller saucepan, heat the milk and butter together (you may also use the microwave)

When potatoes are tender, drain and return to the pot

Using a masher or ricer, mash the potatoes

Add the hot milk and butter and mix until creamy. Test for seasoning and add more salt if needed. If the puree is too stiff, add some more milk and butter. 

Enjoy!