Ingredients

• 2 (7 1/2-oz) jars peeled cooked whole chestnuts, rinsed and drained (2 2/3 cups)
• 2 large leeks (white and pale green parts only), coarsely chopped (1 1/4 cups)
• 1 tablespoon olive oil
• 1 tablespoon unsalted butter
• 1 large onion, coarsely chopped (2 cups)
• 2 celery ribs, coarsely chopped (1 1/4 cups)
• 2 medium carrots, coarsely chopped (1 cup)
• 1 1/2 Turkish bay leaves or 1 California
• 1 tablespoon tamari or soy sauce
• 2 1/2 qt water
• 2 teaspoons salt, or to taste
• 1/3 cup chopped fresh flat-leaf parsley
• 1 teaspoon chopped fresh sage
• 2 tablespoons medium-dry Sherry or Madeira
• 1/2 teaspoon black pepper
• 2 tablespoons olive oil
• 2 tablespoons unsalted butter
• 1/2 sourdough loaf, crust discarded and bread cut into 1/4-inch cubes (4 cups)
• 1 teaspoon chopped fresh sage
• 2 (7 1/2-oz) jars peeled cooked whole chestnuts, chopped (2 2/3 cups)
• 1 teaspoon flaky sea salt (preferably Maldon)

Instructions

1. Put oven rack in upper third of oven and preheat oven to 375°F.
2. Spread chestnuts in 1 layer in a large shallow baking pan, then roast in oven until dry and slightly darkened, about 20 minutes.
3. While chestnuts roast, wash leeks in a bowl of cold water, agitating them, then lift out and drain well.
4. Heat oil and butter in a 5- to 6-quart heavy pot over moderately high heat until foam subsides, then sauté leeks, onion, celery, carrots, and bay leaves, stirring occasionally, until vegetables are pale golden, 8 to 10 minutes. Add chestnuts and tamari and cook, stirring, until most of liquid is evaporated, 1 to 2 minutes. Add water (2 1/2 quarts) and salt and simmer, uncovered, stirring occasionally, until vegetables are tender, about 30 minutes. Remove from heat and stir in parsley and sage. Discard bay leaves.
5. Purée soup in 3 batches in a blender until smooth (use caution when blending hot liquids), transferring to a bowl. Pour purée through a medium-mesh sieve into cleaned pot, pressing hard on and then discarding solids. Bring soup to a simmer and stir in Sherry, pepper, and salt to taste, then remove from heat.
6. Make topping while soup simmers: Heat oil and butter in a 12-inch heavy skillet over moderately high heat until foam subsides, then cook bread cubes with sage, turning occasionally, until croutons are golden, 6 to 10 minutes. Add chestnuts and cook, stirring, 2 minutes. Transfer to a large bowl and toss with sea salt. Ladle soup into bowls and sprinkle each serving with about 1/3 cup topping.
7. Heat oil and butter in a 12-inch heavy skillet over moderately high heat until foam subsides, then cook bread cubes with sage, turning occasionally, until croutons are golden, 6 to 10 minutes. Add chestnuts and cook, stirring, 2 minutes. Transfer to a large bowl and toss with sea salt.
8. Ladle soup into bowls and sprinkle each serving with about 1/3 cup topping.