
In a large bowl, whisk together the flour, sugar, and salt. Cut the butter into the mixture until it resembles coarse meal. Drizzle in water, one tablespoon at a time, until large clumps form. Shape the dough into discs and refrigerate for at least 2 hours.
Roll out the dough, cut into rectangles, and refrigerate. Repeat for second disc.
In a small bowl, mix brown sugar, cinnamon, and flour.
Brush pastry rectangles with egg wash, add filling, and place another pastry on top. Seal edges.
Preheat oven, bake pop tarts until golden brown, then cool.
Mix confectioners' sugar, milk, cinnamon, and vanilla for icing. Spread on cooled pop tarts.