A Balancing Act

• Because carrots contain lots of sugar, with 5 g in one 7-inch long carrot, you need to offset the carrot's sweet taste with bitter flavors. Herbs, including basil and many bitter, leafy green vegetables, provide that balance, and the texture of basil leaves also contrasts with the creaminess of the soup. Finally, any cream, butter or oil in the soup also benefits from the freshness of basil.

Preparing Basil

• Wash the basil well by swishing it in a bowl of water and then rinsing it under running water. Pat it dry with a clean dish towel or with paper towels. For an interesting texture, chiffonade the basil, or cut it in into thin strips or shreds. Do this by plucking off the leaves from a stem and then lay them on top of one another. Then, roll the leaves up lengthwise and then cut across the roll.

Dry vs. Fresh

• Fresh basil adds more of the acidity that carrot soup needs. Classified as a delicate herb, basil loses its fresh, unique and almost minty taste once it is dried. Tasters in a "Cook's Illustrated" taste test stated that the dried herbs -- including basil -- were dusty and stale. To retain basil's freshness, add it to the soup after you have taken the soup off the stove. The best use is to top each bowl individually with the basil chiffonade strips as garnish.

Types of Basil

• As you would expect, lemon basil has a lemon scent and flavor in addition to its "basilness." Since lemon's acidity also pairs well with carrots, lemon basil makes a good substitute for regular basil. Thai basil, with a faint anise or licorice flavor works equally well. Thai cuisine relies on the flavor of Thai basil for its distinct flavor and you'll see Thai basil in soups, noodle dishes and stir-fries.