This is the simplest recipe for chocolate mousse you will ever prepare. There are many variations to this recipe as well. If you wish you can use either milk or white chocolate as well although it is worth remembering that white chocolate is the most difficult to work with.
Sometimes I use some whipped cream in between some layers of chocolate mousse to give a layered effect in the glass. You can add other ingredients to this mousse as well if you wish: chopped nuts, grated orange zest, variety of liqueurs etc.