In a medium bowl, whisk together cornstarch and sugar.

In a saucepan over medium heat, combine the canned peaches, diced ripe mango, the sugar-cornstarch mixture, salt, and peach syrup. Stir continuously for 3-5 minutes until thick and bubbly, then remove from heat and cool to room temperature.

Allow the filling to cool completely to prevent a soggy pastry.

On a lightly floured surface, unfold the puff pastry sheets and roll them out if necessary.

Cut the pastry into equal squares, spoon a generous amount of the cooled filling onto each square, and fold the pastry over to seal.

Place the assembled pies on a baking sheet lined with parchment paper and freeze for at least 6 hours.

For frying, heat oil in a deep skillet to 350°F (175°C). Fry the frozen pies for 3-5 minutes until golden brown.

For baking, preheat the oven to 360°F (180°C). Brush the tops with egg wash and bake on a parchment-lined baking sheet for 18-20 minutes.