First thing first.
Make a mold, or buy one if you can find such a thing.

I made a mold with silli (http://www.sillicreations.com/) and a vodka bottle, shaped like a skull, borrowed from a friend.
He bought the bottle and I just got christmas-light in my eyes and had to try this out.
The silli has to set, which takes around 3-4 hours, and then it will have to post-cure for 3 days (Gasp.. So long waiting time!)

Step 1: The Mold

The silli is firmly attached to the bottle, making sure it covers what needs to be covered.
Dont put it all around, and if you do, make sure you make a cut in the back so you can get the bottle out -
and later the chocolate.

Step 2: Safe!

I wanted to be sure that my skull would be able to stand up when it gets out of the mold, so I patted silli all around.

And as you can see, I made a fine cut in the back and it continues to around the middle in the bottom so be able to take out the bottle.

Step 3: Temperate the Chocolate

Now we can play!

Get your chocolate and temper it.
I use the easy (in my opinion) way;

Melt chocolate and add 1/3 non melted tablets and stir - with care! We do not want air bobbles mixed in.

To check when its perfect;

Make a test and see if it sets, gets shiny, and try to break it - is it a clean "crack" then it should be ready to use.

Step 4:

Pour the ready chocolate into the mold.

I did this 3 times. If you pour to much chocolate in at once it will be grey and the chocolate will go out of temper (such a waste).

First time it is to make a thin skin, when it sets pour once more. For everytime you do so, it will get more sturdy and more easy to handle and can withstand more.

Step 5: Skull!

Once it all sets and you dare to take it out of the mold, do so!

Get your little baby out!
With care! - Well, I did it with care. A shame to start all over, but lucky, the mold can be re-used as many times as you want!

I ended up rubbing my fingers all over, to get imperfections to go away. The heat from your fingers will melt it a bit so you can edit and make a more plain surface.
After that, all you need is to give it a bit of make-up, if needed.
I added some black dust and then gold dust, for the effect. Also with plenty of the gold dust you can add some gold teeth (mayby its a dead pirate?)

All there is now, is to use it as you like! And since its all edible you can also just dig in you teeth and try eating a skull.

Have fun :)