In a large pot, heat a little oil over medium heat. Add the chopped onion and sauté until translucent.

Add the diced potatoes, carrots, and celery to the pot and stir for a few minutes.

Pour in the vegetable broth and bring to a boil. Reduce heat and let it simmer for about 20 minutes, or until the vegetables are tender.

Add the sliced sausage to the pot and cook for an additional 5 minutes.

Season the soup with salt, pepper, and thyme. Stir well and remove from heat.

Ladle the soup into bowls and garnish with fresh parsley before serving.