- 2 cups roasted, shelled, and skinned chestnuts; see how to roast fresh chestnuts (1 lb in shell or 14 oz bottled whole)
- 1 shallot, chopped
- 2 leeks (white and pale green parts only), chopped
- 3/4 stick (6 tablespoons) unsalted butter
- 2 tablespoons dry white wine
- 1/2 fennel bulb (sometimes called anise), stalks and core discarded and bulb coarsely chopped
- 1 cup chicken broth
- 2 1/2 cups water
- 1/4 cup half-and-half
- Coarsely chop chestnuts, reserving 1/3 cup for garnish.
- Cook shallot and leeks in 2 tablespoons butter in a 5-quart heavy pot over moderate heat, stirring, until softened. Add wine and simmer until almost all liquid is evaporated, about 1 minute. Stir in fennel, broth, chestnuts (excluding garnish), and water, then simmer, covered, 20 minutes. Stir in half-and-half and cool mixture slightly.
- Purée mixture in batches in a blender until smooth, transferring to a bowl (use caution when blending hot liquids). Return soup to pot and bring to a simmer, thinning with water if desired. Season with salt and pepper.
- While soup is reheating, heat remaining 4 tablespoons butter in a 10-inch heavy skillet over moderately high heat until foam subsides, then sauté reserved chestnuts with salt and pepper to taste, stirring constantly, until crisp and butter is browned, about 4 minutes.
- Serve soup topped with chestnuts and drizzled with browned butter.