Cut into the chestnut on the curved side and fry in the preheated oven on the middle rack at 200 ° C for about 30 minutes. Let the chestnuts cool and peel them.
Chop the onion and roast it with the chestnuts and rosemary sprig in olive oil for about 2 minutes, stirring constantly. Pour the bouillon and whipped cream on top, season with salt and pepper and cook over a medium heat for about 20 minutes. Remove 4 chestnuts from the soup and set aside for the soup. Take the sprig of rosemary out of the soup, pluck 3 needles off, add to the soup and puree it. Pass the soup through a fine-mesh sieve, reheat if necessary and serve.
Slice the chestnuts that you have set aside and serve as a garnish in the soup. Garnish the soup with rosemary.
Time saving tip:
Prepare soup with pickled chestnuts from the glass.