Heat oven to 400°F. Line a large baking sheet with parchment.
Stir strawberries, sugar, cornstarch, lemon juice, vanilla, and salt in a bowl. Let sit 10 minutes.
Lightly flour your counter. Unroll dough and gently roll to about 1/8-inch thick.
Cut heart shapes with a 3–4 inch cutter. Reroll scraps and cut more until you have pairs.
Whisk egg with water. Brush a thin ring of egg wash around the edge of half the hearts.
Spoon a heaping tablespoon of strawberry filling in the center of each brushed heart.
Top with remaining hearts. Press to seal, then crimp edges with a fork.
Cut a small slit on top for steam. Brush tops with egg wash and sprinkle with coarse sugar.
Chill assembled pies on the sheet for 10 minutes to help prevent leaks.
Bake 18–22 minutes, until deep golden and bubbling. Cool 10 minutes before serving.