1. Melt butter in a large Dutch oven over medium-high heat. Add onion and next 2 ingredients, and sauté 8 to 10 minutes or until tender.
2. Add Marsala, and cook 2 minutes, stirring to loosen particles from bottom of skillet. Stir in vegetable broth, chestnuts, and thyme. Bring to a boil; reduce heat to low, and simmer 20 to 25 minutes or until chestnuts are tender. Discard thyme. Let cool slightly (about 10 minutes).
3. Process soup, in batches, in a blender or food processor until smooth. Return to Dutch oven. Stir in half-and-half and salt and pepper to taste. Cook over low heat, stirring often, 5 minutes or until thoroughly heated. Serve with desired toppings.
*1/4 cup dry white wine and 1 tsp. brandy may be substituted.
**Roasted, peeled fresh chestnuts may be substituted.
Note: We tested with Minerve Whole Chestnuts in Water, which can be found on the baking aisle.