Begin by peeling and dicing the russet potatoes into small cubes. Place them in a large pot filled with water and bring to a boil. Cook until the potatoes are fork-tender, about 15-20 minutes. Drain and let them cool slightly.
Once the potatoes are cool enough to handle, use a potato masher or ricer to mash them until smooth. You want a creamy consistency with no lumps, as this will affect the texture of your Lefse.
In a mixing bowl, combine the mashed potatoes with the butter, heavy cream, sugar, and salt. Mix until well combined. Gradually add 1 1/2 cups of all-purpose flour, mixing until a soft dough forms. If the dough is too sticky, add more flour, a little at a time, until it reaches a workable consistency.
On a lightly floured surface, divide the dough into smaller portions for easier handling. Roll each portion out into a thin circle, about 1/8 inch thick. Dust with flour as needed to prevent sticking.
Preheat your flat griddle or non-stick pan over medium heat. Carefully place the rolled-out dough onto the hot surface. Cook for about 1-2 minutes on each side, or until lightly browned and cooked through. Repeat with the remaining dough.
As you cook each Lefse, stack them on a plate and cover them with a clean kitchen towel to keep them warm and soft.
