Pesto with a French accent flavors hearty, traditional Soupe au Pistou

Big flavored pistou, a Provençal sauce made with basil, garlic, Parmesan and olive oil, gives a delicious kick—and its name—to Soupe au Pistou, a hearty vegetable soup. Recipe below.

Every spring, Marion plants basil based on my best intentions. And every fall, I scramble to harvest the bounty I’ve failed to convert into numerous promised batches of pesto (I think I made it twice this summer). So Sunday afternoon found me, anorak-clad, gathering basil in the rain, fending off bumblebees as I snipped the flowering tops onto the compost pile.

I barely made a dent in the plants in our garden, but our freezer now harbors several zippered bags of pesto, perfect for when we’ll be craving a taste of summer in the dead of winter. And I made some pistou, Provence’s take on Italian pesto, for a pot of Soupe au Pistou.

As with pesto, there are countless variations on pistou. Some are as simple as basil, garlic, olive oil and salt (adding hard cheeses such as Parmesan or pecorino is apparently a fairly recent adaptation—in fact, epicurious.com’s dictionary makes no mention of cheese in its definition). Some versions also include tomato or tomato paste. The key difference between it and pesto is that pistou contains no nuts. Pesto most often is made with pinoli or pine nuts, but my go-to pesto recipe substitutes pecans.

Pistou is a non-cooked sauce or condiment that can be mixed with pasta or spread on bread, but most often, it is used to flavor the soup that bears its name. Soupe au Pistou is a traditional Provençal vegetable soup (but not vegetarian, as it almost always calls for chicken stock—you can make it vegetarian by substituting vegetable broth or using water and salting to taste). Again, recipes vary widely, but include some mix of onions, carrots, beans, green beans, potatoes, summer squashes, tomatoes, pasta and perhaps some hard cheese. You don’t have to add all of these ingredients; the idea is to use what you have at hand for this flavorful, practical soup. The one requirement is pistou. Otherwise, you would just have vegetable soup, and a much less interesting one at that.

Pistou is not unlike the South American chimichurri sauce, made with parsley, garlic, salt and red pepper flakes. Both have a big garlicky kick somewhat tempered by a refreshing herb flavor. Interestingly, when I was talking with a friend from Ecuador about my recipe for chimichurri sauce, which I like to serve over grilled steak or chicken, he said his mother often keeps a similar sauce in her kitchen and stirs it into soups. Small world, right?

Pistou is traditionally made using a mortar and pestle (hence the name for it and pesto). Many cooks frown on using a food processor to make it. I don’t.

Soupe au Pistou
Serves 4 as a light main course, 6 or more as a first course

For the soup:
1 tablespoon olive oil
1 tablespoon unsalted butter
1 medium yellow onion, chopped
1 rib celery, sliced
1 leek, white and pale green part only, halved lengthwise and sliced
2 carrots, sliced
1 large clove garlic, minced
1 teaspoon fresh thyme leaves (or 1/2 teaspoon dried thyme)
5 cups reduced sodium chicken broth (see Kitchen Notes)
1 plum tomato, seeded and chopped
1 cup fresh green beans, cut into 1-1/2″ pieces
1/2 cup cooked white beans (I used canned Cannellini)
1/2 cup cooked red beans (I used canned kidney beans)
salt and freshly ground black pepper, to taste
3/4 cup uncooked small pasta (shells, Ditalini, elbows…)

For the pistou:
3 cloves garlic, roughly chopped
rounded 1/4 teaspoon salt
2-1/2 cups fresh basil leaves, lightly packed
1/3 cup freshly grated good quality Parmesan or Pecorino Romano
6 tablespoons good quality olive oil

Make the soup. Heat a heavy stock pot over medium flame. Add olive oil and butter and swirl to combine as butter melts. Add the onion and celery and cook, stirring frequently, for 5 minutes. You want to sweat the aromatics, not brown them; reduce heat, if necessary. Add leeks and carrots and cook for an additional 2 minutes, stirring frequently. Stir in garlic and thyme and cook until fragrant, about 45 seconds.

Add broth, tomatoes and all the beans. Season generously with pepper, then taste before adding any salt. Store-bought broth and canned beans can be plenty salty. If you add salt, do so sparingly; you can adjust seasonings at the end. Raise the heat to high and bring soup to a boil, then reduce heat to low and simmer, uncovered, for 25 minutes.

Meanwhile, cook the pasta. Time the cooking so it will finish with the soup. When pasta is about 2/3 through its cooking time, drain it and add to the soup pot to finish cooking. This will allow it to impart some (but not all) of its starch to the soup, thickening the broth slightly. It will also allow the pasta to take on the soup’s flavors.

Make the pistou. You can make it while the soup simmers. You can also make it a day or two ahead and refrigerate in a covered container (if you do, let it come to room temperature while the soup cooks). Combine garlic, salt, basil and Parmesan in the bowl of a food processor. Pulse several times to chop and combine ingredients. You may need to scrape down the sides of the bowl with a spatula.

Pour oil over basil garlic mixture. Run food processor until just combined and slightly blended; you want the resulting pistou to still have some texture to it. Again, scrape the sides of the bowl with a spatula as needed.

Serve the soup. Taste and adjust the seasonings. Ladle the soup into four bowls and spoon a generous dollop of pistou into the center of each bowl. Guests should stir the pistou into the soup before eating. Pass the additional pistou at the table. Served with a crusty baguette, soupe au pistou is a satisfying light meal.

Kitchen Notes

Taking stock of your broth. Of course the gold standard is homemade chicken stock; you’ll find Marion’s excellent recipe here as part of her Sweet Potato Vichyssoise. But store-bought chicken broth is getting better. Be sure to look for reduced sodium. If you’d like to make a vegetarian version of this delicious soup, substitute vegetable broth—or simply use water and a generous hand with your salt shaker.