Norwegian Flatbreads

In medium saucepan over high heat, combine potatoes and cold water to cover. Cover and bring to boil, then reduce heat to low and simmer until tender, about 15 minutes. Drain well and force potatoes through ricer or food mill into large bowl. Stir in butter. Add salt and cream and stir until smooth. Add flour and stir until dough forms (do not overmix). Cover and chill at least 6 hours and up to 3 days.
In small bowl, whisk together sugar and cinnamon. Lightly oil 10-inch cast iron skillet and set over moderately low heat. Have ready rolling pin, pastry bench scraper, and thin metal spatula.
Turn dough out onto well-floured work surface. Using pastry bench scraper, cut in half and return half to bowl. Cut other piece in half again; cut 1 piece into 8 small pieces and reserve other piece.
Pat 1 small piece to flatten. Dough may be very soft and sticky, depending on moisture content of potato — add some of 3 cups flour as needed to prevent sticking. Using scraper, flip dough over and pat again to flatten. Roll patty out to 7-inch circle.
Using pastry bench scraper, carefully transfer flatbread to hot skillet and cook until dough bubbles and is beginning to brown underneath, less than 1 minute. Using thin, flexible metal spatula, flip flatbread over and cook other side until lightly brown, about 1 minute. Transfer to plate and brush off any excess flour. Scrape any excess flour out of skillet.
Repeat rolling and cooking with 8 small pieces of dough, then divide remaining piece of dough on counter into 8 pieces and roll and cook each piece. Repeat process with remaining dough in bowl to make 32 flatbreads.
To serve, brush warm lefse with melted butter, sprinkle with cinnamon-sugar, and roll up. Serve warm.