Caramelise 100 g sugar in a pot until golden brown. Add 200 g cream and simmer, stirring occasionally, until the caramel has completely dissolved. Stir in salt and butter in flakes and pour evenly into 6 glasses (each containing approx. 200 ml). Let it cool down.
In the meantime, chop the chocolate and melt it in a bowl over a warm water bath. Remove the bowl from the water bath and let the chocolate cool down. Separate the eggs. Stir egg yolks into the chocolate. Beat egg whites and cream separately until stiff. First fold cream in 2 portions, then carefully fold egg white in 2 portions into the chocolate mixture. Fill the mousse into the glasses on top of the caramel and chill covered for about 1 hour.
In the meantime, caramelise 50 g sugar in a small pot until golden brown. Form caramel with a spoon in thin threads into 4 circles on baking paper. Carefully remove caramel circles from the baking paper and decorate chocolate mousse with them.