In a large pot, heat the olive oil over medium heat. Add the diced onion and sauté for 3 minutes, or until softened and translucent. Stir in the garlic, celery, carrots, potatoes, marjoram, nutmeg, salt, and pepper. Cook for 1 additional minute to blend the flavors.

Pour the vegetable broth into the pot, ensuring the vegetables are fully submerged. Add the bay leaves if desired. Bring the mixture to a boil over medium-high heat.

Reduce the heat to low and partially cover the pot with a lid. Allow the soup to simmer for approximately 20 minutes, or until the potatoes and vegetables are tender.

Carefully transfer about half of the soup to a separate pot. Use an immersion blender to puree the transferred portion until smooth. Alternatively, blend in batches using a traditional blender, being cautious not to overfill it.

Return the blended portion of the soup to the main pot and stir to combine. Add the dairy-free cream or coconut milk and mix thoroughly. Simmer for an additional 2–3 minutes to allow the flavors to meld. Adjust seasoning with additional salt and pepper if needed.

Ladle the soup into serving bowls. Garnish with fresh parsley and, if using, slices of vegan sausage. Serve warm.