Creamy Creamless Butternut Squash Soup

1 celery rib, chopped
1 medium carrot, chopped
1 medium onion, chopped
2 tablespoons fine-quality extra-virgin olive oil
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
1/2 teaspoon dried hot red pepper flakes
1 teaspoons salt
4 cups boiling water ( I USE ONE BOX OF CHICKEN SOUP OR 4 CUPS)

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, pepper flakes and salt. Stir in 4 cups boiling water or broth and simmer, covered, until vegetables are very tender, about 20 minutes.

Purée soup in batches in a blender (use caution when blending hot liquids), adding water to thin to desired consistency.

Makes about 6 cups