Giant Frosted Chocolate Fudge Pop-Tart

1. To make the filling. In a bowl, combine the chocolate, cocoa powder, milk, and butter. Microwave 1-2 minutes, until smooth. Stir in the vanilla. Place in the fridge to cool for at least 20 minutes.
2. Meanwhile, make the dough. In a food processor, combine the flour, cocoa powder, sugar, and butter. Pulse until the mix clumps together and forms pea-size balls. Add 1/2 cup cold water, 1 tablespoon at a time, until the dough comes together and forms a ball. If the dough feels dry, add 1-2 tablespoons additional water.
3. Turn the dough out onto a floured surface and divide in half. Roll each half out into a 1/4-inch thick rectangle, about 8×16 inches. Transfer 1 sheet to a parchment-lined baking sheet and evenly spread on the fudge, leaving a 2 -inch border around the edge. Lay the other half of the dough over the filling and seal the edges by crimping with the back of a fork. Cover the baking sheets and place in the fridge for 1 hour or in the freezer for 20 minutes.
5. Preheat the oven to 400° F. Bake the pop-tart for 30-35 minutes, until set. Cool completely before frosting.
6. Meanwhile, make the icing. In a bowl, whisk together the powdered sugar, cocoa powder, vanilla, and 3 tablespoons water until smooth. Stir in the melted chocolate. If your frosting is too thick, thin with 1-2 tablespoons additional water.
7. Spread the icing over the pop-tart. Let set a few minutes, then top with salt. Let sit 1 hour or overnight to allow the icing to dry. Cut the tart into 9 rectangles. Serve or store in an airtight container for up to 3 days at room temperature.