Break up the compressed yeast and stir into the warm milk. Let stand for a few minutes to dissolve. Sift the flour and salt together into a large bowl. Stir the yeast mixture and egg into the flour and mix into a smooth batter.Stir in the currants, raisins, and apple.Cover the bowl and place in a warm draft free place until doubled in bulk (about 1 hour).Heat the oil in a deep fryer to 375 F. Use two metal spoons to shape scoops of dough into balls and drop them carefully into the the hot oil.Fry 4 of the balls until golden brown (about 8 minutes). Repeat with remaining balls, frying 4 at a time.The doughnuts should be soft and not greasy. If the oil is not hot enough, the outside will be tough and the inside greasy.Drain finished doughnuts on paper towels and dust with confectioners sugar.Serve piled on a dish with more confectioners sugar dusted over them. Serve hot (if possible).