Heat a large saucepan half filled with water. Cut chocolate in pieces and put it in a smaller saucepan or a metal bowl. Put in (or over, depending the size) the heating water. (This technique is called bain-marie; it’s the best way to melt chocolate without burning it).
Separate yolks (and set aside) from egg whites. (The easiest way to do it is by taking the broken egg in one hand and let white fall in a bowl when keeping yolk over your fingers). Add salt and beat the egg whites until stiff.
Add sugar to yolks and beat until they turn white. Put over bain-marie and beat until mixture gets thicker. (It’s very important to use cold eggs (right off the fridge) in order to suceed).
Mix egg cream with chocolate. Pour 1/3 of the stiffen egg whites into mixture and beat smoothly. Add rest of egg whites carefully (you need to mix them without loosing too much of that airy texture, don’t beat!)
Pour into a salad bowl (or various individual cups) and leave in the fridge for a minimum of 3 hours.