Combine potatoes, flour, 3/4 cup butter, sugar, and salt; stir well. Gradually add whipping cream, stirring until well blended.
Roll dough to 1/8-inch thickness on a lightly floured surface; cut with a 4-inch biscuit cutter. Fry on a hot greased griddle. Turn cakes when tops are covered with bubbles and edges are lightly browned. Fold cakes in half. Serve hot with butter.