Heat oven to 420F. Line a baking sheet with parchment paper. Add the egg to a small bowl, beat, then set aside.
Unfold each puff pastry sheet over the parchment paper and cut into 6 rectangles. You should have 12 rectangles total.
Place your coco en almibar in a fine mesh strainer and place the strainer in a bowl to drain excess syrup. If the coconut has too much syrup will spill and spread all over the baking pan while in the oven.
Place 2 tablespoons of strained coconut in the center of each rectangle, leaving about ½ an inch of pastry around the edges.
Brush water on the exposed pastry edges around the coconut and then place the tops of the puff pastry (the remaining rectangles) on the prepared pastry with coconut. Press the edges of the pastelitos so seams are sealed together.
Cut a small slice or poke a couple of holes on the top of the pastry to allow steam out while baking.
Crack an egg into a small bowl and whisk it until well combined and then brush the tops of the puff pastries with the egg.
Completely optional, you can sprinkle a little bit of sanding sugar over each egg-washed pastry before baking.
Bake at 420F for about 21 minutes or until golden brown and puffed up.
While the pastries are baking, make your simple syrup by adding 3 tablespoon of water with 3 tablespoons of white sugar to a cup and microwaving for 1 minute or until the sugar is fully dissolved. Once desolved, add the coconut extract and mix to combine.
Once out of the oven, brush the top with simple syrup and allow to cool.
Allow the pastries to cool off completely before eating.