Mix the flour, salt, and cinnamon together in a large bowl.
Add the yeast, warm milk, egg, apple, raisins and currants and blend well. The dough should feel warm to the touch for the yeast to activate.
Cover and allow the dough to rise for approximately 3 hours.
Heat the oil in a deep fryer or a large deep pan to 170° C.
Drop a large spoonful of dough (1.5-2 tbsp) into hot oil. Do not overcrowd the pan.
Turn doughnuts over (with chopsticks or forks) when brown on one side. Fry until completely brown (about 4-6 minutes) and place on paper towel to let excess oil drain. Repeat with remaining dough.
Dust with powdered sugar before serving.