Preheat the oven to 350 degrees F. Spray a 9x13-inch baking pan with non-stick cooking spray. Set aside.

In a large bowl, mix together the dark chocolate cake mix, water, oil, eggs, and vanilla. Beat on medium speed for 2 minutes. Pour cake batter into greased 9x13-inch baking dish.

Bake for 26-32 minutes, until a toothpick inserted into the center comes out clean.

Remove from the oven and immediately poke holes in the cake using the end of a wooden spoon.

In a medium bowl with a tight-fitting lid, shake together 2 cups of milk and 1 package of chocolate fudge pudding mix. Shake until just slightly thicked then immediately pour over the cake, making sure to get as much pudding as possible in the holes. Use a spatula to spread pudding over the cake.

Remove the lid from the hot fudge sauce then microwave for about 45 seconds until the sauce is melted. Pour over cake. Use a spatula to spread to the edges.

Allow cake to cool then refrigerate for at least 2 hours.

In a medium bowl with a tight-fitting lid, shake together 1 1/2 cups of milk and 1 package of chocolate fudge pudding mix. Shake until pudding thickens, about 3 minutes.

Stir Cool Whip into chocolate pudding, making sure it is completely combined. Spread topping on the cold cake.

Run a vegetable peeler along the long side of Hershey's Special Dark chocolate bar to make chocolate curls. Finely chop any remaining chocolate with a sharp knife.

Sprinkle chocolate curls all over the top of the cake.

Refrigerate at least 2 hours or overnight before serving.