
In a large bowl, whisk together the flour, sugar, and salt. Cut in the butter until the mixture resembles coarse meal.
Drizzle the ice water over the mixture and stir until it forms large clumps. Gather into a ball, flatten into discs, wrap in plastic, and refrigerate.
Roll out one disc of pastry and cut into rectangles, place on a baking sheet, and refrigerate.
Repeat with the second disc of pastry. Fill half with the cinnamon-brown sugar mixture, then top with another pastry rectangle and seal.
Poke holes in the tops for steam, brush with egg wash, refrigerate again, and then bake until golden.
Whisk together the icing ingredients and drizzle over cooled pop tarts.