You have to have the fingers of one hand touching the wrist of the other, then put your fingers into the wholes of the apple and twist your hands back to a normal position. It's the most satisfying thing.
Try a karate chop. Twist the stem off, put your middle knuckle of your index finger right over the hole and then make a fist and pound it down right on your finger.. Sounds like it hurts but really doesn't if you get it in one chop