Add butter, sugar, salt, and flour to a food processor and pulse until coarse crumbs form.
Add ice water through the feed tube until dough forms (may not need all).
Cover and chill 1 hour.
Line a baking sheet with parchment paper.
Remove dough from refrigerator and roll into 1/4" thick on a floured surface.
Cut into 2 1/2" x 4” even rectangles.
Place half of the dough rectangles on parchment-lined baking sheet.
Add 1 tablespoon of strawberry jam to the middle of each dough rectangle.
Top with remaining dough and seal edges with a fork.
In a small bowl, beat egg well with 1 tablespoon of water to create the egg wash.
Brush the top of each tart and poke 6 small holes in each one using a small pairing knife or fork.
Bake at 375° F for 15–20 minutes or until golden. Let cool.
Whisk glaze ingredients (powdered sugar, lemon juice, milk, and salt) together.
Drizzle over cooled pop tarts and top with sprinkles, if desired.