Break the chocolate and Mars bar in pieces. Put them in a bowl and melt over a bowl with hot water, or carefully in the microwave.

Whisk the egg yolks with the sugar and salt until puffy. Mix this with the chocolate melt and let cool some.

Whisk the cream until hard. Stir 1 dl of the whipped cream and carefully add the rest. Pour the chocolate mousse in serving glasses and put in the fridge to cool.
Add some pieces of chocolate as garnish.