Begin by peeling the potatoes. Choose starchy type potatoes. Boil the potatoes until they are soft and easily pierced with a fork. Drain the potatoes and let them cool slightly. Mash the cooked potatoes. Add the butter and mix it well. Allow the mashed potatoes to cool to room temperature.
In a large mixing bowl, combine the mashed potatoes, softened butter, milk, and salt. Gradually add the flour, mixing well until the dough comes together. You may need a little more or less flour to achieve the right consistency, which should be soft but not overly sticky.
Dust a clean surface with flour, which prevents sticking, and divide the dough into small, manageable portions. Roll each portion into a ball and then flatten it slightly with your hands.
Using a rolling pin, roll out each portion into thin, round sheets. Lefse should be paper-thin, so aim for an even, delicate consistency.
Heat a griddle or a large skillet over medium-high heat. Carefully transfer each lefse to the hot griddle or skillet. Cook for about 1-2 minutes on each side or until you see light brown spots. It should puff up a little while cooking. Remove from the griddle and stack the lefse on a clean kitchen towel. Cover them with the towel to keep them warm and pliable. Lefse can be served in various ways. A typical way to roll a hot dog in it. Spread a bit of butter on a warm lefse and sprinkle with cinnamon and sugar for a sweet treat. Pair lefse with your favorite jam or preserves for a fruity delight. Enjoy it savory-style with smoked salmon, a dollop of sour cream, and fresh dill. Lefse also makes an excellent wrap for sliced cheese and cold cuts.