Cook the vegetables: Heat olive oil in a Dutch oven (or large saucepan) over medium heat. Add shallot, carrot, and celery. Cook, stirring regularly, for 5-7 minutes or until vegetables are softened.
Add the garlic: Add in the garlic and cook for one minute.
Add additional ingredients: Stir in the chestnuts, thyme, bay leaf, vegetable stock, and salt and pepper.
Cook the soup: Bring to a boil and let it simmer for 15-20 minutes or until all the vegetables are fork-tender.
Puree the soup: Discard the bay leaf. Using an immersion blender, carefully puree the soup until it is creamy.
Add the heavy cream: If using, stir in the heavy cream. Bring it to a quick rolling boil. Give it a quick taste and add more if necessary.
Add the nutmeg: Right before serving, stir in the grated nutmeg.
Serve: Ladle into individual bowls and if preferred, garnish with your choice of toppings.