Heat the avocado oil in a large soup pot over medium high heat. When hot, add the sliced sausage and fry, stirring occasionally, until browned, 5-7 minutes. Remove the sausage from the pot and set aside in a medium bowl.
Add the ghee to the pot and melt over medium heat. Add the onion, potatoes, celery, and carrots. Stir occasionally for 8-10 minutes until vegetables have softened and onion is translucent.
Add the broth, sausage, sea salt and pepper to taste, and stir to combine. Increase the heat to medium high and bring to a boil. Reduce the heat to low and simmer for 30 minutes until the vegetables are tender.
Stir in the kale and simmer until slightly wilted, about 5 minutes. Ladle the soup into bowls and serve hot. Store leftovers in a covered container in the refrigerator for up to 5 days.
