Preheat a large saucepan.
Heat the duck fat or olive oil in the saucepan. Add the butter.
Add the onions and sauté for 2 mins.
Add the leek and carrot and sauté for 2 mins.
Add the red wine and vegetable stock. Bring soup to the boil and then simmer for 8-10 mins.
Add the herb before removing soup from heat.
Ladle the soup into bowls and serve.