Preheat Oven: Preheat your oven to 375°F.
Mix Filling: In a bowl, mix the chopped pecans, melted butter, brown sugar, dark corn syrup, and cinnamon.
Prepare Puff Pastry: Roll out a sheet of puff pastry and cut it into rectangles.
Score Pastry: Lightly score a smaller rectangle inside each piece without cutting all the way through. This will help the edges puff up when baking.
Add Filling: Spoon a couple of tablespoons of the pecan mixture into the center of each rectangle.
Egg Wash: Brush the edges with a whisked egg. You can mix the egg with a bit of milk if you like.
Cinnamon Sugar: Mix the granulated sugar with the cinnamon. Sprinkle this mixture over the edges where you brushed the egg wash.
Bake: Bake in the preheated oven for about 15 minutes, or until the pastries are golden brown on top and bottom. Baking time may vary slightly depending on your oven.