I learned how to make chocolate mousse from a children's Ladybird Library book in the 70's. It was 2oz chocolate per egg.
That's it! The best mousse recipe ever. Melt the chocolate (I use 50% milk, ie 30% and 50% dark, ie 85%) and supermarket eggs. Melt the chocolate and separate the eggs.
Whisk the egg whites until stiff. Allow the melted chocolate to cool and add the yolks then fold the chocolate/yolk mix into the egg whites and decant into ramekins or one large serving bowl. Refrigerate til set.
Scale up or down, make for one or twenty. It is the best. I make it all the time and haven't killed anyone yet.