Make the Chocolate Spiders:

1. Melt dark chocolate in the microwave, stirring every 30 seconds until smooth.
2. Pour into spider mold cavities and place in the fridge until set.

Bake the Cake:

1. Preheat the oven to 350°F.
2. Spray a 13×9-inch pan (or disposable pan) with baking spray.
3. In a large bowl, mix cake mix, pudding mix, eggs, and oil until smooth. Fold in mini chocolate chips.
4. Pour into the prepared pan and bake according to cake mix instructions.
5. Let the cake cool completely.

Make the Frosting:

1. Beat softened butter and cream cheese until creamy. Add powdered sugar and vanilla and mix until fluffy.
2. Spread about ¾ of the frosting over the cooled cake. Reserve the rest for the border. (If you’d like less frosting on the cake, just use as much as you’d like and save the rest for another project.)

Decorate:

1. Sprinkle glittery sugar over the frosting for a magically spooky shimmer.
2. Melt more dark chocolate and pour into a squeeze bottle.
3. Pipe spiderwebs directly onto the cake: start with a plus sign, add an X over it, then swoop curved lines between the spokes to form webs.
4. Carefully unmold chocolate spiders and place them between the webs.
5. Tint the remaining frosting with gray food coloring until you get a medium spooky shade.
6. Pipe a border using a 1M star tip. Sprinkle mini chocolate chips over the border for texture.