Brown Sugar and Cinnamon PopTarts

for the crust:

2 1/2 cups flour
1 tsp salt
1 tsp sugar
1 cup butter, cold and cut into pieces
1/4 cup cold water

for the filling:
1/2 cup brown sugar
1 1/2 tsp cinnamon
4 tsp flour
1 egg

for the glaze:
1/4 cup powdered sugar
1 tsp cinnamon
3-4 tbsp milk

Preheat oven to 350. 
Place the flour, salt and sugar in a food processor and pulse until just combined. Add in the butter and pulse until it forms a coarse crumb-like mixture.
With the food processor on, slowly add the cold water just until a dough forms. Do not process for more than 30 seconds.
Turn the dough out onto a work surface and divide it in half, wrapping each half in plastic wrap. Refrigerate for an hour.
Remove the dough from the refrigerator and allow to sit for 15 minutes. Then, roll out one half on a lightly floured surface to about 1/8 inch thickness. Trim the edges to make a rectangle.
Slice the dough into 9 rectangles and place onto a silicone (or parchment paper) lined baking sheet. Repeat with the second half of the dough to make the top half of the PopTarts.
In a small bowl, stir together the brown sugar, cinnamon, and flour, then set aside.
Whisk the egg and brush it onto the bottom pieces of the PopTarts.
Place a heaping spoonful of the cinnamon filling on each of the rectangles and spread across evenly, leaving a slight edge clear around the dough.
Place the remaining 9 rectangles on top of the filling and press along the edges to seal. Use the tines of a fork around the edges to completely seal. Prick the tops of the PopTarts with a fork to allow for escaping steam while baking. Brush the tops of the PopTarts with the remaining egg mixture.
Bake for 20-25 minutes or until the PopTarts are golden brown.
Cool completely on a wire rack. While the PopTarts are cooling, make the glaze. In a small bowl, whisk together the powdered sugar, cinnamon, and milk.
Once the PopTarts are lukewarm, spread the glaze over the tops.