In a food processor, combine the flour, cocoa powder, sugar, and salt. Pulse to blend the dry ingredients.

Add the cold butter and pulse until the mixture forms coarse crumbs, about the size of peas.

Add 4 tablespoons of ice water and pulse. Add more water, one tablespoon at a time, just until the dough starts to clump together. Do not let it form into a full ball. It should hold together when pressed between your fingers.

Turn the dough out onto a surface, shape into a disk, and wrap in plastic wrap. Chill for at least 1 hour or overnight.

In a small saucepan or microwave-safe bowl, heat the heavy cream until warm.

Pour over the chocolate chips and let sit for a minute, then stir until smooth. Add powdered sugar, cocoa powder, and coffee flavoring. Stir until thick and glossy.

Remove the dough from the fridge and let it sit at room temperature for about 15 minutes so it is easier to roll.

Place on a lightly floured surface and roll into a rectangle about 12 by 10 inches.

To portion evenly, cut the dough into rectangles that are approximately 3 by 5 inches. This will give you evenly sized pop tarts.

Place half of the rectangles onto a parchment paper lined baking sheet.

Whisk the egg in a small bowl.

Brush egg wash around the edges of each bottom piece of dough.

Add about 2 tablespoons of filling to the center and gently flatten it slightly.

Place a second piece of dough on top. Press around the edges with your fingertips to seal, then crimp with a fork.

For clean edges, use a bench scraper or sharp knife to trim if needed.

Bake in a preheated oven at 350°F for about 20 minutes.

The tops should look set and slightly firm.

Transfer to a wire rack and let cool completely before glazing.