In a mixing bowl, mix the sifted flour and the baking powder. Form a well with the flour.
In the middle, add the whole eggs, half of the beer. Whisk it all until a very thick paste.
Add the remainder of the beer. In a separate bowl, whisk the egg whites to hard peak. Fold in the beaten egg whites to the batter.
Dip each slice of apple in the batter making sure that it coats all of the apple. Deep fry at 350 F, when you see a good coloration on the bottom half of the apple (they will float), flip them on the other side until identical coloration.
Remove from the fryer on a plate with paper towels to absorb the frying oil.
Sprinkle with powdered sugar and serve hot with a side of the chocolate sauce as a dipping sauce.