Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a mixing bowl, combine flour, salt, and sugar. Add cold, cubed butter and mix until the mixture resembles coarse crumbs.
Gradually add ice water, mixing until the dough comes together. Divide the dough in half, wrap in plastic wrap, and refrigerate for 30 minutes.
On a floured surface, roll out the dough to about ⅛ inch thick. Cut into rectangles.
In a small bowl, mix brown sugar, cinnamon, and flour for the filling. Spoon a small amount onto half of the rectangles, leaving space around the edges.
Place another rectangle of dough on top and press the edges with a fork to seal. Poke a few holes on top to allow steam to escape.
Bake for 20-25 minutes or until golden brown. Let cool completely.
For the glaze, mix powdered sugar, vanilla extract, and milk until smooth. Drizzle over the cooled pop tarts.