Thaw the puff pastry sheets (let them sit at room temperature) for about 30 minutes, or until they’re soft enough to unfold without tearing.
Preheat your oven to 400°F. Line two baking sheets with parchment paper and set them aside.
Lightly flour your work surface, then roll out each puff pastry sheet with a rolling pin until it measures roughly 12x18 inches.
Slice each sheet in half lengthwise, then cut into thirds crosswise to create six even squares. Set the squares aside while you prepare the filling.
In a small bowl, whisk together one egg and one tablespoon of water to make an egg wash. Keep it nearby for later.
In another small bowl, stir the turbinado sugar and cinnamon together until evenly combined.
For the filling, whisk the pumpkin puree, brown sugar, pumpkin pie spice, and the remaining two eggs in a medium bowl until smooth and fully blended.
Place a generous spoonful of filling in the center of each puff pastry square.
Fold each square in half diagonally to form a triangle. Press the edges together, then crimp with a fork to seal tightly.
Brush the tops of the turnovers with the egg wash using a pastry brush.
Sprinkle each one with the cinnamon-sugar mixture for extra flavor and crunch.
Bake for 18-20 minutes, or until the pastries are puffed and golden brown. Let them cool slightly before serving.
Serve and enjoy!