01 - In a large mixing bowl, whisk together flour, sugar, and salt. Add cold cubed butter and cut in using a pastry blender or fork until the mixture resembles coarse breadcrumbs.
02 - Gradually add ice water while stirring just until dough begins to come together. Turn onto a lightly floured surface, knead gently, and form into a disk. Wrap in plastic wrap and refrigerate for at least 30 minutes.
03 - Preheat oven to 400 degrees Fahrenheit. Line a baking sheet with parchment paper.
04 - In a small bowl, mix strawberry jam with diced fresh strawberries until evenly combined.
05 - On a floured surface, roll out chilled dough to approximately 1/8 inch thickness. Using a heart-shaped cookie cutter measuring 3 to 4 inches, cut out 16 hearts total.
06 - Place 8 dough hearts on the prepared baking sheet. Spoon approximately 1 tablespoon of strawberry filling onto the center of each heart, maintaining a half-inch border.
07 - Brush the edges of filled hearts with beaten egg mixed with water. Top each with a remaining heart and press edges firmly to seal. Crimp perimeter with a fork to create decorative pattern.
08 - Brush the top surface of each pie with egg wash and sprinkle generously with coarse sugar.
09 - Using a sharp knife, cut a small slit in the top center of each pie to allow steam to escape during baking.
10 - Bake for 18 to 22 minutes until the pastry is golden brown. Remove from oven and cool slightly before serving.