Step 1 Heat the oil in a large saucepan over medium heat and saute the leeks and carrots about 3 minutes.
Step 2 Add the garlic and saute an additional 1 minute, stirring occasionally.
Step 3Add the chicken broth, potato and one-fourth teaspoon salt and simmer about 15 minutes, until the vegetables are tender. Add the zucchini during the last 10 minutes of cooking.
Step 4Puree with an immersion blender or in a food processor until smooth. Allow to cool, then chill the soup in the refrigerator.
Step 5Season to taste with salt and pepper. Stir in the chopped basil. Pour the soup into serving bowls and garnish each with a few strips of basil.