Melt the butter in a large pot and gently cook the onion with a pinch of salt until very soft, about 10 minutes.
Stir in the garlic and then add the carrots and chicken broth.
Bring to a boil, then cover and simmer for 20 minutes or until the carrots are very tender.
While the soup is cooking make the dukkah. Toast the sesame, coriander, cumin and fennel seeds in a dry frypan over a low heat, stirring constantly, until fragrant, for approximately 3 minutes. Add the hazelnuts, seeds, salt and pepper to a food processor and blend to a coarse mixture. You could also use a mortar and pestle.
Let the soup cool a little and then puree with a stick blender until very smooth. Add salt and pepper to taste.
Tope each bowl with a dollop of yoghurt and a sprinkle of dukkah and parsley.