3 pounds parsley with tops), tops discarded and root peeled and chopped
12 inch thyme leaves
5 tablespoons butter unsalted
6 cups water
0.5 teaspoon pepper white
Equipment
bowl
pot
blender
peeler
Directions
Cook onion and garlic in butter in a large heavy pot over medium heat, stirring occasionally, until onion is softened and golden, 6 to 8 minutes.
Add parsley root, thyme, bay leaf, white pepper, and 3/4 teaspoon salt and cook, stirring occasionally, until parsley root begins to soften, 8 to 10 minutes.
Add water and broth and simmer, partially covered, until parsley root is very tender, 30 to 40 minutes.
Discard thyme and bay leaf and stir in oil. Purée soup in batches in a blender until smooth (use caution when blending hot liquids), transferring to a bowl. If soup is too thick, thin to desired consistency with water. Season with salt, then return to cleaned pot to keep warm, covered, until ready to serve.
Shave chestnuts with an adjustable-blade slicer or sharp vegetable peeler as thinly as possible over each serving.
Soup, without chestnuts, can be made 2 days ahead and chilled, uncovered, until cool, then covered. Reheat over low heat, thinning with water if necessary. Shave chestnuts over soup just before serving.