Melt the chocolate with the half-and-half in the microwave. (it should take about 1 minute or so).
Separate the egg yolks from the egg whites. Mix 3 egg yolks with the melted chocolate mixture. Add the vanilla extract, and mix. Let it cool down.
Whip the 4 egg whites with a pinch of salt, using an electric mixer, always turning in the same direction (so as to not break the egg whites), first on low speed, and then on higher speed. About half way through, add the granulated sugar and continue whipping.
Once the chocolate mixture is cold, add it to the whipped egg whites. Gently and slowly, mix the chocolate with the egg whites. Take your time. You do not want to break the egg whites, so it is important you mix slowly and gently. You are done once you have a uniform smooth chocolate mousse.
Put the chocolate mousse for at least 2 hours in the fridge. Serve cold in dessert cups. Enjoy!
Optional: you can add nuts for decoration. (I added a walnut).