Instructions Start by making the fudge filling. Stir together cocoa powder, brown sugar, milk or cream, salt and half of the chopped milk chocolate. Place in a small sauce pan and cook over medium heat, stirring, until chocolate is melted. Cook mixture at a low boil, stirring occasionally for 5 minutes. Remove pan from heat, add remaining chocolate, butter and vanilla and stir until smooth. Set aside to cool and thicken. Preheat the oven to 400 degrees F. Line baking sheets with parchment paper or silicone baking mats. In a large mixing bowl, combine the flour, cocoa powder, sugar and salt. Add chunks of the butter and mix with a pastry blender or your fingers until the mixture is crumbly. Gradually add the water until the mixture is moistened and a dough forms. Place the dough in between two large sheets of parchment paper or on a lightly floured surface and roll out into an 1/8-inch thickness, using the parchment paper or working on a lightly floured surface. Cut the dough into rectangles, about 6 1/2 x 4 1/2 inches. Place a heaping tablespoon of filling on one half of the rectangle. Lay the other half of the dough over the filling and seal the edges by crimping with the back of a fork. Repeat until all the dough has been used, saving the scraps and re-rolling to make more rectangles. Bake the pop tarts for 10 to 12 minutes. Cool completely While the poptarts cool make the frosting. In the bowl of stand mixer, mix the powdered sugar, meringue powder, vanilla, cocoa powder and 3 tablespoons water for about 7-10 minutes on medium speed, until peaks begin to form. Stir in the melted chocolate. If your frosting seams too thick, thin as needed for outlining or flooding by adding more water. I found 5 tablespoons of water was good. Spoon a thin layer of the frosting on top of cooled poptarts. Allow frosting to harden 10 minutes and then if desired sprinkle with, course salt or course, sugar. Place on a baking sheet and allow the tart to harden uncovered, about 2 hours.