Add the flour, sugar and salt to a food processor and pulse a few times to evenly combine. Add the butter and shortening and pulse about 8 times, just enough to cut butter into smaller pieces. With the processor running, pour ice cold water down the feed tube and pulse until the dough begins to clump together.

Turn the dough onto a floured surface and gather into a ball. Divide into 2 even portions and flatten or roll each portion into an approximate 6-inch disc and wrap tightly with plastic wrap. Chill at least one hour in the refrigerator.

Line two baking sheets with parchment paper and set aside. Remove 1 disc of dough from the refrigerator and let rest 10 minutes to soften (keep the other disc in the refrigerator).

On a lightly floured cutting board, roll the dough into a rectangle larger than 9x12 inches in order to create nine 3x4 inch rectangles. Transfer these rectangles to a baking sheet and refrigerate.

Brush egg wash over the edges of the second set of rectangles, add Nutella down the center, and sprinkle with brown sugar and cinnamon.

Remove the other baking sheet from the refrigerator and brush all surfaces with egg wash. Place on top of the Nutella rectangles and seal the edges.

Freeze pastries for 30 minutes. When ready to bake, brush tops with egg wash and bake at 350°F for 25 to 30 minutes.

Let cool for 5 minutes, then transfer to wire rack. Whisk together glaze ingredients and spread on cooled pastries.