- 1 celery rib, chopped
- 1 medium carrot, chopped
- 1 medium onion, chopped
- 2 tablespoons fine-quality extra-virgin olive oil (preferably Tuscan) plus additional for drizzling
- 1 lb winter squash such as butternut, peeled, seeded, and cut into 1/2-inch cubes
- 1/2 lb boiling potatoes, peeled and cut into 1/2-inch cubes
- 1 whole fresh peperoncino (small hot Italian green pepper) or 3/4 teaspoon dried hot red pepper flakes
- 2 teaspoons coarse sea salt
- 3 1/2 cups boiling water plus additional for thinning
- 1 crisp amaretto (Italian almond macaroon), finely crushed (2 tablespoons)
- Cook celery, carrot, and onion in 2 tablespoons oil in a 3-quart heavy saucepan over low heat, stirring occasionally, until tender but not browned, 10 to 12 minutes. Add squash, potatoes, peperoncino, and sea salt. Stir in 3 1/2 cups boiling water and simmer, covered, until vegetables are very tender, about 20 minutes.
- Remove and discard peperoncino (if using pepper flakes, leave in soup). Purée soup in batches in a blender (use caution when blending hot liquids), adding more water to thin to desired consistency.
- Serve soup drizzled with additional oil and sprinkled with amaretto crumbs.