Whip the Debic Parfait until you have a smooth mousse.
Add the Granny Smith purée and continue to mix briefly.
Fill half-sphere Silpat(r) moulds with the apple parfait.
Put in the freezer.
Finely chop the pistachio nuts.
Stick 2 half-spheres of apple parfait together and roll in your hands to create a nice, smooth ball.
Roll through the finely chopped pistachios.
Store the balls in the freezer.