Peel and wash potatoes. Next, quarter potatoes lengthwise. Lay each half side-by-side on the cutting board and slice across both at 1/2' to 3/4" intervals. Thickness may determine length of cooking time.
Place cut potatoes in a large saucepan, covering with at least 1-1/2" of COLD water above the surface of the potatoes. Sprinkle even with the salt.
Bring potatoes to a boil over HIGH heat. Once it begins to boil rapidly, turn it down to MED to MED-HIGH heat. Set the timer for about 15 minutes. Stir occasionally while boiling. At this point, check to see if a large potato cube flakes apart easily. If it's still a little tough, boil an extra 2-3 minutes. Drain.
Put potatoes in a mixing bowl and begin to mash and break apart the rest of the potatoes using a potato masher, mixer beaters or a the head of a whisk.
Add the HOT milk and begin to blend in with the hand mixer.
Add 1 T of the softened butter at a time until melted and mixed in.
Mix in the sea salt and freshly ground black pepper, if desired.
Enjoy!