This is a hearty Italian classic known as Ribollita. To make the prep easier, you can chop the vegetables and refrigerate them (separately) the night before.
The soup can be refrigerated up to 3 days in advance.
8 to 10 servings (makes 16 cups)
2 tablespoons extra-virgin olive oil
1 large yellow onion, cut into 1/2-inch pieces
2 leeks, white and light-green parts only, cut into quarters, then thinly sliced and rinsed well
2 medium carrots, scrubbed well and cut crosswise into thin rounds
2 ribs celery, chopped into 1/2-inch pieces
2 cloves garlic, coarsely chopped
Two 15.5-ounce cans no-salt-added cannellini beans, drained and rinsed
7 cups water
3 tomatoes, seeded and cut into 1-inch pieces
1 medium zucchini, cut into 1-inch pieces
1 cup peeled butternut squash chunks, cut into 3/4- to 1-inch pieces
10 leaves lacinato kale, stemmed and cut into 1 1/2-inch pieces, (1 1/2 to 2 cups; may substitute curly kale)
Leaves from 6 sprigs fresh thyme
1/2 teaspoon kosher salt, plus more as needed
1/2 teaspoon freshly ground black pepper, plus more as needed
1 large starchy potato, peeled and cut into 3/4- to 1-inch chunks
1/2 packed cup basil leaves, thinly sliced, for garnish
Heat the oil in a large saucepan or soup pot over medium-low heat.
Add the onion, leeks, carrots, celery and garlic and cook for 10 minutes, stirring occasionally, until softened. If the vegetables start to brown, reduce the heat.
Meanwhile, place half the cannellini beans in a food processor.
Add 1/2 cup of the water and puree until smooth.
Add the tomatoes to the saucepan; increase the heat to medium and cook for 8 minutes, stirring often, then add the zucchini, squash, kale and thyme.
Reduce the heat to medium-low and cook for 5 minutes, then add the salt and pepper, the remaining 6 1/2 cups of water, the pureed beans and the potato.
Increase the heat to medium-high and bring to a boil, then stir in the remaining beans.
Reduce the heat to low, cover and cook for about 10 minutes, stirring occasionally, until the squash and potato are barely fork-tender.
Taste and add salt and/or pepper, as needed.
Add the basil and serve hot.