Separate eggs. Beat the egg whites until soft peaks form. Add sugar and beat until stiff.
Beat the egg yolks and sour cream in a second bowl. Add flour and salt and stir the dough until smooth. Slowly mix in a third of the egg whites, fold in the rest. Melt some butter in the pan over medium heat. Bake pancakes from 2-3 tablespoons of batter. As soon as the dough is firm, turn and bake the second side until golden brown. Gradually add butter to the pan and bake more pancakes. Keep the finished pancakes warm.