I love chilled vegetable soup purees when the weather turns warm. The key is to know the basic principles: Purees require liquid (usually stock), vegetables and a thickening agent (more vegetables). There's no need for flour, because you can control the thickness of the soup by adding more or less stock.

The other secret to great pureed soup is what you use to puree it. There are a few different options: the blender, the immersion hand blender or the food processor. My two standbys are the blender or the immersion blender. If you prefer a frothy, cream-like texture without using any dairy, you will have good success using a high-powered blender.

I go for the immersion hand blender when I am pressed for time. It goes right into the soup pot and purees the soup so you don't have to transfer the soup to another vessel. Make sure when you use it to always keep the wand on the bottom of the pan when pureeing so it doesn't fly up and decorate your ceiling.

Cooking butter lettuce with leeks and zucchini yields a fresh mix of flavors and textures. Classic lettuce soup is usually a blend of potatoes and lettuce. This lighter, modern take on classic French lettuce soup includes mint and zucchini, both of which have a natural affinity with lettuce.

The leeks give a bit of added sweetness to the soft textured zucchini. Sour cream is the only dairy here, added just as a garnish. You can leave it out if you want a non-dairy soup. I like to serve the soup in small white bowls for a pretty presentation. This soup is also excellent warm.

Chilled Butter Lettuce and Zucchini Soup with Fresh Mint

Serves 4

For the soup:

2 tablespoons olive oil or grapeseed oil

2 leeks, cleaned and light green and white part only, finely chopped

1 1/2 pounds (about 6 medium) zucchini, sliced

1 head butter lettuce, cored and shredded

2 garlic cloves, minced

3 tablespoons coarsely chopped mint

5 cups chicken stock

Salt and white pepper, to taste

1 tablespoon fresh lemon juice

To garnish:

1/4 cup sour cream

1 tablespoon finely chopped mint or whole mint leaves

1 tablespoon finely chopped chives

1. Heat the oil in large saucepan over medium-high heat. Add leeks and saute, stirring occasionally, for about 3 5 minutes or until softened. Add the zucchini and saute for 5 minutes, or until lightly browned and slightly softened. Add lettuce and saute until it is wilted, about 3 minutes. Add garlic, and saute another minute. Add the mint and stock. Bring the soup to a boil, and reduce heat for soup to a simmer. Cover and simmer for 20 minutes.

2. Place the soup in a blender, or use a hand immersion blender, and process until pureed. Add the salt, pepper and lemon juice, and taste for seasoning. Transfer to a serving bowl, cover and refrigerate soup for about 4 hours or until chilled; taste for seasoning right before serving.

3. To serve, pour soup into bowls and garnish with sour cream, chopped mint and chives.

(Diane Rossen Worthington is an authority on new American cooking. She is the author of 18 cookbooks, including "Seriously Simple Parties," and a James Beard Award-winning radio show host. You can contact her at www.seriouslysimple.com.)