Wash and peel the potatoes. Cut the potatoes into 1" cubes, then place them into a large saucepan. Fill the pot with cold water so that it covers the potatoes by an inch.
Add one teaspoon of kosher salt to the saucepan. Bring the water to a boil, and boil for about ten minutes, or until the potatoes are soft enough that they can be easily pierced with a fork.
Drain the water. Add the butter and a pinch of salt, and mash the potatoes using a potato masher.*
Switch to a spoon, and stir in the milk. Taste, and season with more butter or salt if desired. If you prefer a creamier consistency, add another tablespoon of milk.
Serve warm, and enjoy!
Notes
*If you do not have a potato masher, transfer the potatoes to a large mixing bowl and use a hand mixer with the whisk attachments to whisk the potatoes, butter, and salt together instead. Then whisk in the milk.*This can also be done in the bowl of a stand-up mixer. Use the paddle attachment on medium speed to "mash" the potatoes, butter, and salt for about a minute. Switch to the whisk attachment, and whisk the milk into the potatoes on medium speed for about a minute until super smooth and creamy.