Stir in yeast mixture, mix to a firm dough, knead for 5 minutes.
Cover, stand in warm place for about 1 hour or until dough is doubled in size. * Knead dough until smooth, gradually knead in small pieces of the soft butter. * Place dough into prepared pan and stand in warm place about 40 minutes or until doubled in size.
Bake at 200 °C (400 °F) for 20 minutes.
Reduce heat to 180 °C (350 °F), bake further 40 minutes, covering loaf with foil if beginning to overbrown.
Stand for 5 minutes, then turn onto a wire rack to cool.
Dust with sifted icing sugar just before serving, if desired.