Roughly chop the nuts. Roast in a pan without fat. Sprinkle with sugar and let it caramelize. Spread nut caramel on baking paper and let it cool down.
Chop the couverture and melt in a hot water bath. Leave to cool lukewarm, stirring from time to time. Soak the gelatine in cold water.
Stir the quark, vanilla sugar and cinnamon until smooth. Whip the cream until stiff. Squeeze the gelatine and dissolve at low heat. First stir 3 tbsp. quark into the gelatine, then stir the mixture into the remaining quark.
First stir 3-4 tablespoons of whipped cream into the couverture. Then stir in the quark mixture and finally fold in the remaining cream.
Crumble brittle. Set aside a third of it. Fold the rest of the brittle into the mousse. Pour into a bowl and chill for at least 6 hours. Before serving, spread the rest of the nuts on top.