4 tbsp. butter
1 medium onion, roughly chopped
1 carrot, peeled and roughly chopped
1 rib celery, roughly chopped
1 clove garlic, roughly chopped
Kosher salt, to taste
1 24-oz. bottle peeled cooked chestnuts, drained,
or 1 1/2 lbs. peeled roasted chestnuts
1/3 cup crème fraîche
Freshly ground black pepper, to taste
1 tbsp. dry sherry, such as amontillado
1. In a 4-qt. saucepan, heat butter over medium heat. Add onions, carrots, celery, and garlic. Season with salt and cook, stirring occasionally until tender and lightly browned, about 20 minutes. Add 6 cups water, chestnuts, and salt; simmer over medium-low heat until chestnuts are tender, 45 minutes.
2. Purée soup with an immersion blender or in batches in a regular blender. Whisk in crème fraîche, black pepper, and sherry. Season with more salt to taste. Serve hot.