Heat the oil in a large soup pot and add the onions, carrots, and celery. Cook vegetables until the start to become tender.
Add fennel seed and cook a few minutes more.
Add warm broth and bring to a boil.
Add sausage, garlic, and chopped herbs, and bring to a boil again.
Reduce heat and simmer on low just until vegetables are tender and flavors are rendered, about 15-20 minutes.
Add zucchini and simmer for about 5-10 more minutes.
Just before serving, add the kale and stir until it is wilted and mixed into the soup.
Serve with lemon wedges, and a sprinkle of nutritional yeast or a good grated hard cheese.