To make the filling, put the strawberry jam and finely chopped fresh strawberries into a saucepan and heat over medium heat for 2-3 minutes. Stir periodically.
While the strawberries are heating, whisk the cornstarch with 1 tsp vanilla and 1 TBSP water until smooth. Add the cornstarch mixture to the jam. Cook over medium heat for another 4-5 minutes until thickened. Remove from heat.
Roll out one pie dough on a floured surface. Roll into a rectangle as much as you can. Using a pizza cutter, cut the dough into 6 even rectangles. Repeat with second pie dough roll so that you have 12 rectangles.
Place 6 rectangles on a baking sheet (that is covered with parchment paper). Spoon 1-2 tablespoons of the strawberry jam mixture into the middle of each pastry. Spread the filling around but be sure to leave border around the edges to seal the pastries.
Cover each square with the remaining dough squares. Crimp all the way around the pastries with a fork to seal them.
Brush the top of the pastries with the egg wash.
Bake for 14-16 minutes at 375 degrees. Cool on a baking rack.