Heat the olive oil over medium heat in a large pot. Add the leeks and celery, and cook for about 5 minutes until softened. Add the parsnips and cook for 2 minutes, then add the garlic and nutmeg and cook 30 seconds longer. If at any point the leeks begin to brown too quickly, reduce the heat to medium low to prevent them from burning.

Add the vegetable stock to the pot and scrape up any brown bits from the bottom and sides of the pan. Add the bay leaf and thyme and bring to a boil. Reduce the heat to medium low and simmer for 15-20 minutes or until the parsnips are tender.

Remove from heat and purée the soup until smooth using an immersion blender, or in 1-2 batches in a blender or food processor. If using a blender or food processor, place the puréed soup back in the pot. Add 1-2 cups more vegetable stock or water as desired to make the soup the desired consistency.

Stir in the heavy cream, then season with salt and pepper to taste. Serve warm with additional thyme leaves if desired. Enjoy!