I arrived in France in late summer, and in one respect a hot vegetable soup may seem a strange dish to be preparing in August or September—it is still quite hot in the South of France that time of year. But it really isn't so odd when you consider that the evenings are beginning to cool down a bit and that even if the day is warm, the preparation of the soup doesn't heat up the house—only one burner is required and the soup can quietly simmer as the day winds down.
Furthermore, when you consider the ingredients in Soupe au Pistou, there could hardly be a more appropriate dish to prepare during the final months of summer. Soupe au Pistou can contain the full array of the bounty of the late summer market all in one bowl. Some recipes have only green beans (haricot verts), shell beans (Coco Blancs and/or Coco Rouges) , summer squash and the pistou. But the renditions that I like the best, include much more—potatoes, carrots, tomatoes and the first of the winter squash. Versions like this are truly a celebration of the moment. When I made some this past weekend, every single vegetable in my soup came from my farmers' market or my garden. (In the interest of full disclosure, I should admit that the shell beans I used came from my farmers' market via my freezer. I haven't seen any at the market yet this year and it really isn't Soupe au Pistou without the shell beans.)
I have given very precise measurements for the vegetables in my recipe—I am getting ready to teach this soup and need to have exact quantities so I can make a specific amount to serve—but in practice, this should be a relaxed soup to make. To obtain enough soup for 6 people (about 3 quarts) you will need a total of about 2 cups onions and/or leeks, 6 to 7 cups of vegetables, and 1 to 1 1/2 cups of fresh shell beans (or cooked dried beans). I think that roughly equal quantities of each of the vegetables that you are using is best, but you should use what you have. As I mentioned, to be a true Soupe au Pistou, you should probably make sure that you do include green beans and summer squash.
How you cut the vegetables is also up to you. Some recipes call for diced vegetables. This is my personal preference and I like to calibrate the size of my dice to the size of the shell bean I am using. Alice Waters in Chez Panisse Vegetables suggests using the tip of your little finger as a size guide. Other recipes call for sliced vegetables. The most important thing is for everything to be uniformly sized.
Very traditional recipes for Soupe au Pistou simply direct you to place all of the vegetables in a pot, cover them with water and then simmer until they are all tender. The green vegetables suffer under this treatment, so many recipes tell you to wait to add the green beans and summer squash (and any other green vegetables that you might choose to add) until the last 20 minutes or so of cooking (when the fresh shell beans and root vegetables are just barely cooked). In the finished soup, these vegetables added towards the end will still be fully cooked, but they will also be recognizable.
When I make this soup, I prefer a more modern approach of softening the onions and leeks (and garlic, should you choose to include some in the soup itself) in some olive oil before adding the other vegetables and the water. I think soups that start with this step are always more flavorful since it gives these aromatic vegetables a moment to infuse the fat with their flavor. Since fat carries flavor, this gives the finished soup a greater depth.
I haven't yet mentioned the addition of the pasta at the end, but this too is a traditional addition to Soupe au Pistou. Most often it is elbow macaroni that is used, but occasionally it will be small shells or, my favorite, orzo. The pasta is usually added for the last 10 to 15 minutes of cooking. If the soup is being made a day ahead, cook the pasta separately and add it to the soup when you will be serving it. Pastas left to sit in soups overnight tend to become quite bloated as they continue to absorb liquid.
The final addition of the pistou is of course what really makes this simple vegetable soup stand out. In addition to the basil and garlic, it usually contains Parmesan and sometimes finely diced peeled and seeded tomatoes. Many recipes include tomatoes in the soup itself, adding them with the green beans and summer squash, but they tend to disintegrate and fade into the soup when added this way. I love the bright red flecks and fresh flavor that the tomatoes contribute when they are added as part of the pistou. Most traditionalists will prepare the pistou in a mortar & pestle...but I take the heretical step of preparing mine in the food processor (it is just so much easier).
As for serving the pistou, you could stir it into the whole pot of soup just before serving it, but many people (myself included) prefer to pass the pistou in a small bowl and allow diners to add as much or as little as they like. It is quite strong with garlic. Those unfamiliar with it should be allowed to introduce themselves to it gradually.
That first batch of Soupe au Pistou that I made in France was a bit of a disappointment. As I sat down to eat it I was aware that it was unaccountably bland. It contained wonderful vegetables grown in the soil of Provence, but I had failed to add enough salt as the soup cooked to help them release their full flavor. The pistou also suffered from my timidity with the salt (and possibly the garlic too). Pistou can handle quite a bit of salt—as much as a teaspoon for the size recipe given below—so, don't be timid when you make your pistou! As for the soup itself, as you make yours, salt with each successive addition of vegetables and liquid, tasting carefully each time—you will probably use less salt when you salt this way and your soup will be anything but disappointing.
Soupe au Pistou
(Recipe adapted from Simple French Food by Richard Olney)
4 T. Olive oil
2 medium leeks, white and tender green parts only, halved lengthwise and cut into a 1/4-inch dice or sliced 1/4-inch thick—about 1 1/2 to 2 cups (make sure that the leeks are well-rinsed)
6 oz. onion (1 medium), diced—about 1 cup
6 oz. carrots (2 medium), diced—about 1 cup
10 oz. butternut squash, diced—about 1 cup
12 oz. potatoes, peeled and diced—about 1 1/2 cups
1 lb. (before shelling) fresh cranberry beans in the pod, shelled to make 1 1/2 cups shelled beans (see note)
Several sprigs of thyme, tied together with a piece of cotton kitchen twine
2 quarts water
6 oz. green beans, topped and tailed and cut into 1/2-inch lengths—about 1 1/2 cups
8 oz. small zucchini, diced—about 1 1/2 cups
1 scant cup small macaroni or a heaped half cup orzo (3 1/2 oz. pasta)
1 recipe pistou
Salt & Pepper, to taste
For the soup, heat 4 T. olive oil in a large stockpot over medium heat. Add the leeks and onions along with a generous pinch of salt. Sweat for 5 minutes or so—until the onions and leeks are wilted and just beginning to turn translucent. Add the carrots, butternut squash, potatoes and fresh shell beans and continue to cook for a minute or two.
Add the bundle of time along with 2 quarts of water. Bring to a boil. Add salt to taste and simmer for 20 minutes. Add the zucchini and the green beans.
If necessary, add more water. Bring the soup back to a simmer. Cook for 10 minutes. Add the pasta (again, adding more water if the soup seems too thick) and cook until the pasta is cooked and the vegetables are all very tender—another 10 minutes or so. Taste the soup and salt as necessary. The soup may be served immediately, or do as some Provençal cooks do and allow the soup to sit off the heat for up to an hour before reheating to serve. The soup may thicken upon standing, so add more water if necessary. The soup should be served hot with the Pistou passed separately so that each diner can swirl it into their soup to suit their taste. Makes 3 quarts, serving 6 to 8.
Note on the Shell Beans: Traditionally Soupe au Pistou is made with fresh Coco Blancs or Coco Rouges (or a combination of the two) shell beans. In the Midwest the closest that I have been able to find to the Coco Rouges are fresh cranberry beans (they may even be the same thing). But any fresh shelling bean from your farmers' market would be fine in this soup. If fresh shell beans are unavailable, you may use a dried bean. White navy beans are similar to Coco Blanc bean (sometimes called French Navy Beans), so that is the dried bean I would choose, but dried Cannellini or Cranberry beans would work too. To use dried beans in the soup, soak half to 2/3 cup of the dried beans of your choice overnight. Drain the beans and rinse. Place in a sauce pan and add water to cover by an inch. Bring to a simmer. Add a tablespoon of olive oil to the water and continue to cook until tender—an hour to an hour and a half, depending on the variety of bean chosen. Add salt to taste when the beans are half cooked. If not using right away, store the beans in the refrigerator in their cooking liquid. To add the beans to the soup, add them along with their cooking liquid, when the green beans and zucchini are added.
4 cloves of garlic (about a tablespoon crushed)
2 cups packed basil leaves (about 2 ounces), washed and dried
½ to ¾ c. extra virgin olive oil
1 cup finely grated parmesan (3 oz.)
8 oz. ripe tomatoes (2 med.), peeled, seeded and finely diced (when seeding the tomato, work over a sieve to collect the tomato juice—add this juice to the soup as it cooks)
Salt, to taste
To make the Pistou, smash the garlic, along with a pinch of salt, to a paste using the flat of a chef's knife or a mortar and pestle. Place this in the food processor with the basil and a small amount of the olive oil. Process until the basil is almost puréed, adding just enough olive oil to facilitate this process. Scrape the basil and garlic purée into a bowl. Stir in the cheese, the tomatoes and the remaining olive oil. Season to taste with salt. Set aside while the soup cooks to allow the flavors to blend.