Preheat oven to 425°F. Line a baking sheet with parchment paper. Set aside.
In a medium bowl, combine apples, brown sugar, flour, cinnamon, vanilla and lemon juice. Toss until apples are well coated. Set aside.
Over a lightly floured surface, roll puff pastry into a 14" circle (approx.).
Transfer rolled out dough onto prepared baking sheet.
Place apple mixture into the pastry, leaving a 2" boarder.
Gently fold edges of pastry over filling, leaving much of the apples still exposed.
Brush the folded edge of pastry with the beaten egg. Sprinkle with coarse sugar if desired.
Bake for 20-25 minutes or until the crust is golden brown.
Remove from oven. Serve warm a la mode. Enjoy!