Mix water and cornstarch together and set aside.
Place remaining ingredients in a pot. Bring to a simmer, then slowly mix in cornstarch slurry. Let cool.
Once mixture cools, place a spoonful into each square of puff pastry and fold over. Crimp with a fork and repeat until all are filled.
Refrigerate for at least 25 minutes.
Preheat oven to a 375°.
Brush with egg wash and sprinkle sugar on top.
Bake for 20–25 minutes until golden brown.