Chocolate mousse {for easter}

I'm not sure if the hollow sugar coated chocolate eggs are available all around the world... but if not i'm sure you can use the hollow chocolate eggs.  I thought this would be a nice dessert for easter to bring in the theme.

What you need:
4 eggs, separated
125 ml castor sugar
25 ml strong coffee
200g dark chocolate
100g unsalted butter chopped into blocks

To start I recommend you "prepare" your eggs :-) by just hitting off the top of the egg with a knife {softly}

Turning the egg around as you hit it until it comes off.

First mix the egg yolk and the castor sugar until it becomes thick and lighter in colour.  
Then mix in the coffee.  
Melt the chocolate over hot water on the stove {double boiler}.  
As soon as the chocolate is melted, start adding the butter one block at a time, until a smooth cream is formed. 
Now mix the chocolate to the egg-yolk mixture.  
Beat the egg whites until stiff, then fold into the chocolate mixture.  
Let the mixture rest in the fridge for about 30min before dishing into the eggs {the mixture is then less runny}

Refrigerate for at least 6 hours.

Enjoy!