Preheat oven to 350°F and prepare a 9x13-inch baking dish with non-stick spray.
Mix and bake the chocolate cake according to the box directions.
Let the cake cool for 10 minutes, then use the end of a wooden spoon to poke holes all over the cake.
In a bowl, whisk together chocolate pudding mix and milk until thickened, about 2 minutes.
Pour the pudding over the cake, letting it seep into the holes.
Refrigerate for 15-20 minutes to allow the pudding to set.
Spread whipped topping evenly over the chilled cake.
Drizzle with hot fudge and chocolate syrup. Sprinkle with mini chocolate chips.
Refrigerate until ready to serve.