Make the Strawberry Filling:

Cup of Yum
1. In a saucepan over medium heat, stir together the strawberries, sugar and water until the sugar is dissolved. Heat the mixture to boiling, stirring often. Reduce heat and add lemon juice. 3/4 cup quartered strawberries, 1/3 cup granulated sugar, 1/4 cup water, 1/2 tablespoon lemon juice
2. In a small cup, combine the cornstarch and two tablespoons of water. Mix well. Pour this into the boiling strawberry mixture. Stir and boil over medium-low heat for 4 minutes or until the mixture has thickened a bit. Remove the pan from the heat. 2 teaspoons cornstarch, 2 tablespoons water
3. Add the vanilla and butter. Mix until the butter has completely melted. Allow the mixture to cool for 15 minutes, then add the last 1/2 cup of quartered, fresh strawberries. Cool completely.* 1/2 teaspoon vanilla extract, 1 tablespoon salted butter, 1/2 cup additional quartered strawberries

Make the Strawberry Turnovers:

1. Preheat the oven to 400ºF. Gently unfold the puff pastry sheets and cut each sheet into 9 squares. 1 box (2 sheets) Pepperidge Farm Puff Pastry Sheets
2. Spoon 2-3 strawberry pieces in the center of each square, draining most of the syrup as you do this. (You can use the leftover strawberry syrup to make a glaze.)
3. Fold the puff pastry square to make a triangle and then use the tins of a fork to press the pastry closed along the two open edges.
4. In a small bowl, whisk together the egg and water. Use a pastry brush to spread the egg wash on top of the puff pastry triangles. 1 large egg, 1 tablespoon water
5. Sprinkle a bit of granulated sugar overtop the egg wash and place the pastries on a large baking sheet lined with a silicone baking mat or parchment paper. 1/4 cup granulated sugar
6. Bake for 12-13 minutes until the turnovers are golden brown. Then remove from the oven and allow the turnovers to cool. 
7. If desired, add two tablespoons of the leftover strawberry syrup to 1/2 a cup of powdered sugar and whisk together until smooth. Drizzle the glaze overtop the cooled pastries. 1/2 cup powdered sugar for glaze