Frosted Brown Sugar Cinnamon Pop Tarts

In a food processor, pulse flour, sugar, and salt to combine.
Add cold cubed butter; pulse until the mixture is crumbly.
Drizzle in the ice water and pulse just until the dough looks pebbly but holds when pressed.
Divide dough into 2 equal sections, wrap each tightly in the shape of a disc, and chill for 1 hour.
On a lightly floured surface, roll each section to 1/8–1/4 inch thick (the thinner the better) into around 13 x 11 inch rectangle; trim edges to make it even.
Cut each rectangle into 8 smaller rectangular pieces (about 3 x 4.5 inches) for 16 total.

In a bowl, mix together brown sugar, all-purpose flour, melted butter, cinnamon, vanilla, and a pinch of salt until evenly combined.

Brown butter (optional): Melt butter in a light-colored pan over medium heat, stirring, until it foams and turns golden with a nutty aroma. Remove from heat and cool slightly. (You can also use regular melted butter.)
Whisk powdered sugar, maple syrup, brown butter (or melted butter), cream, vanilla, and cinnamon until smooth. Set aside.

Line a baking sheet with parchment. Arrange 8 dough rectangles spaced apart.
Add about 2 tablespoons of filling to each, spreading flat and leaving clean edges.
Whisk egg and cream for the egg wash. Brush edges of each bottom rectangle.
Top with another rectangle, press to seal, and crimp edges with a fork.
Poke holes across the tops with a fork for steam vents. Brush tops with egg wash.
Chill the assembled Pop-Tarts in the fridge for 20 to 30 minutes on the baking sheet. Meanwhile, preheat oven to 350°F.
Bake 20 minutes until lightly golden.
Transfer pop tarts to a cooling rack and let cool 10 to 15 minutes, then cover tops with icing. Allow to set before serving.