Preheat oven to 400 degrees. Line a large baking sheet with parchment paper and set aside.
Unroll both pieces of thawed puff pastry, cut each one into four squares (you'll have eight total pieces).
In a medium sized bowl, combine the chopped apple, sugar, flour, and cinnamon and mix until everything is well combined.
Spoon the apple filling into one corner of the puff pastry (about 1/4 cup for each piece), fold the other corner over, then crimp with a fork to seal.
Brush each turnover with the egg white.
Bake at 400 degrees for 15-18 minutes, or until lightly golden brown.
Remove from the oven and set aside to cool.