This soup is based on a favorite autumn dish where roasted acorn squash halves are filled with a white bean mixture and drizzled with an herby sauce. It's a delicious and satisfying dish that just happens to be vegan. It also translates well into this soup, a delectable combination of sweet vegetables (roasted squash, leeks) and creamy beans, punctuated with a dollop of fresh, zingy, garlicky, herby pistou.
First, what is pistou and why not pesto? A pistou is an uncooked French sauce, similar to a pesto in that a fresh herb (or herbs) are ground with garlic and olive oil into a rough paste. From there recipes vary considerably. Some use basil only, while others combine herbs like I do here. Some add cheese or tomatoes, some use more oil. I use pistou instead of pesto mostly because I like this as a vegan (and nut-free!) soup, but of course you could use pesto if you wished.
I also like the fresh taste of the pistou when it is added at serve up, allowing the warmth of the soup to release the flavors of the herbs without cooking them. The pistou is potent, too, so only add a small dollop to each bowl.
1 butternut squash, about 2-1/2 pounds 4 large cloves garlic, unpeeled grapeseed oil (or other neutral oil) 1 large leek (about 2-1/2 cups chopped) 6 cups flavorful chicken or vegetable broth 4 cups of cooked white beans salt and freshly ground pepper For the pistou: 1/2 (heaping) cup of chopped parsley 1 (scant) cup of chopped fresh basil 1 tablespoon chopped fresh rosemary 1 tablespoon fresh thyme leaves 1 smallish garlic clove, chopped 1/4 cup olive oil salt
Preheat oven to 400 degrees. Halve, peel, seed and chop the squash into 1/2-inch cubes. Place on a baking sheet along with the unpeeled garlic cloves, drizzle with grapeseed oil and roast in oven until squash is just tender and starting to color, about 30-45 minutes.
Meanwhile, trim off and discard the tough dark green leaves of the leek. Cut the leek in half lengthwise and rinse off under running water to remove any grit. Slice the leeks into 1/4-inch half moons. You should have about 2-1/2 cups.
Drizzle about 1 tablespoon of grapeseed oil into a large pot or dutch oven. Add the leeks with a pinch of salt and sauté gently over medium heat until wilted. Add broth and bring to a gentle simmer. When squash is done, remove from oven and set the garlic aside. Using a slotted spoon (to drain off any excess oil) transfer squash to the soup pot and add the beans. Squeeze the garlic from its skin and add to the pot. Taste and add salt and pepper as needed. Bring to a gentle simmer to heat through but do not boil or cook for a long time as the beans and squash should remain whole.
To make the pistou: Combine herbs, garlic and olive oil with a pinch of salt in a food processor and pulse until blended. The texture should remain fairly rough, so don't make a smooth paste. Alternatively, chop the herbs, garlic and a pinch of salt together on a chopping board until well-combined. Put into a bowl and stir in the olive oil.
To serve: Ladle the hot soup into bowls and dollop a little pistou on top (it goes a long way!)
Notes: • It's OK to use canned or jarred beans here, or cook up a batch of beans if you have the time and inclination. • You can use your favorite brand of store bought pesto as a short cut. • Use a more flavorful broth (rather than a thin stock) for this soup as it doesn't spend a lot of time simmering with the vegetables. I recently used a store-bough roasted chicken stock that was perfect. Vegetable stocks are great too, and will keep this soup vegan. You may want to add a spoonful of miso towards the very end of cooking for added savoriness. • I use butternut squash here because I find it easiest to work with but you can use any dense winter squash in this recipe. Red Kuri would work well, for example. See our winter squash guide for more information, here.