Cut the chocolate into small cubes and place in a small saucepan with 100g of cream. Heat over low heat with a whisk, stirring constantly, until the chocolate has melted.
Remove the pan from the heat and carefully stir the mixture with the whisk until smooth. Then stir the yoghurt thoroughly into the warm chocolate mass with the whisk and pour everything into a cool mixing bowl to cool (at room temperature).
Beat the rest of the cream with the powdered sugar until stiff and mix carefully but thoroughly into the cooled chocolate mixture in portions (the mixture may still be lukewarm).
Put the ice cream mass in the ice cream maker for 10-15 minutes. Then transfer to a freezer and leave to freeze for another 2 hours.