- 1 medium leek (white and pale green parts only), chopped
- 1 medium russet (baking) potato
- 1/2 cup chopped shallot
- 2 tablespoons unsalted butter
- 1 tablespoon olive oil
- 2 bunches Chinese celery (1 1/2 lb total), top leaves discarded and stalks cut into 2-inch pieces
- 1/2 cup dry white wine
- 4 cups chicken stock or low-sodium chicken broth (32 fl oz)
- 1/2 cup heavy cream
- 1/2 teaspoon salt
- 1/4 teaspoon black pepper
- 6 (1/4-inch-thick) diagonal baguette slices
- 1/4 cup extra-virgin olive oil
- Kosher salt to taste
- Garnish: fresh Chinese parsley leaves or flat-leaf parsley leaves
- Wash leek well in a bowl of cold water, then lift out and drain well. Peel and chop potato. Cook shallot in butter and oil in a 3-quart heavy saucepan over moderate heat, stirring, until softened, about 2 minutes. Add leek and cook, stirring, until softened, about 5 minutes. Add celery and potato and cook, stirring, 2 minutes. Add wine and boil 1 minute. Add broth and simmer, covered, until celery is very tender, about 1 hour.
- Purée soup in batches in a blender until very smooth (use caution when blending hot liquids), then pour through a large medium-mesh sieve into a bowl, pressing hard on solids. Discard solids. Transfer soup to cleaned saucepan, then stir in cream, salt, and pepper and heat over low heat until hot. Thin with water if desired.
- Preheat oven to 350°F.
- Brush baguette slices with oil and season generously with kosher salt and pepper. Arrange in 1 layer on a baking sheet, then bake in middle of oven until golden brown and crisp, 12 to 15 minutes.
- Serve soup topped with croutons.