1.    Crumble the pumpernickel, mix with the walnuts and spread on a baking sheet with baking paper. Roast in the oven for 10 minutes at 150 degrees top and bottom heat.
2.    Melt the chocolate in a double boiler. Add the Pumpernickel nut mixture to it and stir everything well. Then spread the crumbly mixture on the baking tray again and allow it to cool.
3.    Quarter the pears and remove the core. Dice the fruit flesh and place in a pan. Sprinkle the sugar over it and, while stirring, let it caramelise in the pan. Place aside to cool.
4.    Beat the buttermilk in a bowl with the mascarpone. Fold in the sugar and agar-agar.
5.    Now, alternatingly, layer the three components in a glass. Keep aside a little of the Pumpernickel crumble as a topping.
6.    Store in a cool place for at least an hour. Prior to serving, sprinkle the remaining crumble over the dessert.