Line 2 sheet trays with parchment paper and whisk one egg with a dash of milk
Roll out one of the thawed (if using frozen) puff pastry sheets on a lightly floured surface (or silicone baking mat) into a 28 cm / 11 inches square. Cut it into 4 equal squares.
If the dough warms up and becomes difficult to handle, refrigerat for 10 minutes, otherwise continue with a light egg wash on the edges of each square.
Then, place about 1-2 tablespoons of filling in the center. Pay attention not to touch the edge with the filling.
Fold one corner of the puff pastry over the filling to the opposite corner, creating a triangle. Press your finger around the edges to properly seal them then crimp with a fork
If the pastry is still nice and cold, apply a light egg wash then sprinkle with a small amount of granulated sugar
Place the unbaked turnovers in the fridge for 15 minutes while pre-heating the oven to 190C / 374F (no fan)
Bake the Apple Turnovers for about 30 minutes or until the top is golden brown and the bottom is evenly baked
Let them slightly cool in the baking tray for 5 minutes then move them onto a cooling rack
Serve them fresh. Any leftover can be stored at room temperature for 2-3 days