Start by cutting the cold butter into cubes.

Prepare the dough by combining the flour, sugar, salt, and cubed butter and combining with your hands, breaking up the butter clumps. Then add the cold water and mix until it forms a dough.

Refrigerate the dough for 45 minutes. Otherwise, it will be too soft to roll out.

While the dough is chilling, prepare the filling. Finely chop the apples and add them to a pan over medium heat. Add the butter, brown sugar, cinnamon, vanilla, and salt. Cook for 5-7 minutes, stirring occasionally until the apples have softened.

Use an immersion blender to blend the filling. Then add the cornstarch and cook the filling for another 2-3 minutes, until the filling thickens.

Roll out the pop tart dough over a clean, lightly floured surface. Cut out 5 by 7 inch rectangles. You should make 16 rectangles, making 8 pop tarts.

Place 8 dough rectangles on a lined baking sheet, place a dollop of filling in the center, and enclose with another dough rectangle.

Seal the pop tart with a fork, then cut off the excess edges (optional). Poke 3 small holes on the top of each pop tart using a fork. Lightly brush maple syrup, on top of the pop tarts, substituting for egg wash.

Bake the pop tarts for 20 minutes at 350*F/ 175*C.

While the pop tarts are baking, whisk together the frosting ingredients until combined.

Once the pop tarts have baked and have fully cooled off, top them with the frosting, sprinkle extra cinnamon on top, and enjoy!