1 tablespoon butter
1 tablespoon extra-virgin olive oil
1 medium onion, chopped
1 stalk celery, chopped
2 cloves garlic, chopped
1 teaspoon chopped fresh thyme or parsley
5 cups chopped carrots
2 cups water
4 cups reduced-sodium chicken broth, “no-chicken” broth or vegetable broth
1/2 cup half-and-half (optional)
1/2 teaspoon salt
Freshly ground pepper to taste
Add onion and celery; cook, stirring occasionally, until softened, 4 to 6 minutes. Add garlic and thyme (or parsley); cook, stirring, until fragrant, about 10 seconds.
Stir in carrots. Add water and broth; bring to a lively simmer over high heat. Reduce heat to maintain a lively simmer and cook until very tender, about 25 minutes.
Puree the soup in batches in a blender until smooth. (Use caution when pureeing hot liquids.) Stir in half-and-half (if using), salt and pepper.