1- Separate the egg yolks from white. In a large salad bowl, whisk together the yolks and the sugar until the mixture gets clearer and smooth.
2- Cut the chocolate and butter in small squares and put them in a small heavy saucepan with 2 spoons of Cointreau and 2 spoons of water. Melt the whole over a low heat, stirring non stop with a wooden spoon until smooth. The chocolate must not stick to the pan.
3- Pour the melted chocolate in the egg and sugar mixture and stir ; add the left spoon of liquor, mix, add the cream and stir.
4- Beat the egg whites with an electric mixer until frothy. They must get quot;hardquot; (the real test is to turn the bowl upside down and the whites should not fall down !!!).
5- Spoon by spoon (quarter by quarter) , gently incorporate the egg whites to the chocolate mixture; you can do it simply with a whisk (you just need to do quick and light moves, you must not quot;breakquot; the bubbles kept in the whites).
6- Evenly pour the mousse in the 4 souffleacute; dishes (you can as well use 6 to 8 ramequins to serve more guests). Leave in fridge for at least 3 hours before serving (the mousse should get quot;hardquot;).
Decorate with orange strips, a teaspoon of sour cream or coffee beans...