Whisk together the granulated sugar, flour, and cocoa powder in a large mixing bowl.
Once the dry ingredients are combined, use a fork, pastry cutter, or food processor to mix in the butter until the butter is broken up into small, pea-sized pieces.
Whisk in the water until a dough forms. Work the dough into a ball and then cover it with plastic wrap. Chill the dough in the fridge for 20 minutes while the oven preheats to 350°F.
In a small mixing bowl, whisk together the cream cheese, ¼ cup of powdered sugar, and finely crushed Oreos.
Roll your dough out into a sheet about ¼ inch thick on a lightly floured surface. Use a knife to cut the dough into rectangles about 3x4 inches.
Add a large spoonful of filling to half of your rectangles and then top them with the other half so the rectangles sandwich the filling. Use a fork to crimp the edges. Bake your pop-tarts for 14 minutes.
Let the pop-tarts cool for about 15 minutes in the fridge. While your pop-tarts cool, prepare your frosting by whisking together the remaining powdered sugar and the milk until smooth.
Spoon the frosting over your pop-tarts and then sprinkle on the roughly crushed Oreos. Serve and enjoy!