Cut puff pastry sheet into 3 equal rectangles along the fold lines of the pastry (as you know the pastry is folded in 3 parts, so just separate those three). Cut each rectangle into 8 or 9 triangles.
Chop apple finely, mix with brown sugar and cinnamon. Let apples sit to get juicy.
To make each wizard hat: place 1 triangle on foil or parchment paper. Fill with a little bit of chopped apples. Place another rectangle on top, seal the edges with your fingers. Elongate the top portion of the “hat” and bend it to the side. Fold bottom portions of the triangles up to form a hat brim. Brush the top portion of each hat with egg wash. Sprinkle hats with cinnamon and sugar.
Line baking sheet with parchment paper. Transfer hats to baking sheet. Bake for about 20 minutes until hats puff up and get golden brown.