1 egg beaten with ½ tsp water for egg wash, optional
For the optional vanilla glaze
½ cup icing sugar
1½ tsp water
½ tsp vanilla extract
Method
Preheat the oven to 230°C.
Meanwhile, pit the peach and dice it into small pieces (about ½-inch cubes).
Unfold the first sheet of thawed pastry and use a rolling pin to gently roll over any perforations or indentations. Use your fingers to gently seal any torn spots. Roll the pastry into a square shape, about 9x9 inches, then use a very sharp knife to cut the pastry sheet into 4 equal squares. Repeat with the second sheet of pastry.
Divide the diced peaches evenly between the 8 squares of pastry, placing them in the middle of each piece. Top the peaches in each pastry with ½ tablespoon of peach preserves. Fold each piece of pastry over the filling to form a triangle, gently pressing the edges together with your fingers. Then, use a fork to seal the edges.
Line a cutting board or large plate with parchment paper and transfer the shaped turnovers to it. Chill the turnovers in the refrigerator for 10 minutes.
Slide the parchment with the chilled turnovers onto a large baking sheet. Brush the egg wash onto the tops of the turnovers, if desired. Use a sharp knife to cut two small slits into the top of each of the pastries.
Bake the turnovers until golden brown, about 20 minutes.
Allow the turnovers to cool for at least 10 minutes. Meanwhile, if desired, make the vanilla glaze: In a small bowl, whisk together the icing sugar, water, and vanilla. Drizzle the turnovers with the vanilla glaze, and enjoy.