Makes about 2 1/2 to 3 Quarts
Fresh borlotti beans (also known as cranberry beans) are available seasonally and worth the little extra effort it takes to shell them. Depending on how full the pods are, buy about 2 to 2 1/2 pounds of beans to yield the 4 cups needed here. If you can’t find fresh borlotti beans, use one pound dried kidney beans, soak overnight, drain, and add with the carrots, celery, and potatoes.
- 1/2 cup extra-virgin olive oil
- 2 medium leeks, white and light green parts, halved lengthwise and sliced
- 1 medium onion, chopped
- 1 tablespoon kosher salt
- 1/2 teaspoon crushed red pepper flakes
- 2 medium carrots, peeled and chopped into 1/2-inch pieces
- 2 celery stalks, chopped into 1/2-inch pieces
- 2 medium russet potatoes, peeled and cut into 1/2-inch dice (about 1 1/4 pounds)
- 2 tablespoons tomato paste
- 2 fresh bay leaves
- 4 cups shelled fresh borlotti beans
- 2 medium zucchini, chopped into 1/2-inch pieces (about 3/4 pound)
- 1 medium head escarole, coarsely shredded (about 8 cups)
- 4 cups loosely packed fresh basil leaves
- 1/4 cup pine nuts, toasted
- Freshly grated Grana Padano, for serving
Heat a large Dutch oven over medium heat. Add 1/4 cup of the olive oil. When the oil is hot, add the leeks and onion. Season with 1 teaspoon of the salt and the crushed red pepper flakes. Cook until leeks and onion have wilted but not colored, about 6 minutes.
Increase the heat to medium high and add the carrots, celery, and potatoes. Cook, stirring occasionally, until the potatoes begin to stick to the bottom of the pot, about 5 minutes. Make a space in the pan and add the tomato paste. Cook and stir in that spot until the tomato paste is toasted and darkens a shade or two. Increase heat to high. Add 5 quarts cold water and the bay leaves. Bring to a boil, uncovered. Let it cook vigorously to reduce and homogenize the flavors of the soup base, about 30 minutes.
Add the beans and zucchini and cook until beans are almost tender, about 30 minutes more.
Add the escarole, and cook until it is tender and the soup is thick and flavorful, about 30 minutes more. Season with the remaining 2 teaspoons salt once the beans are cooked through. Remove bay leaves.
When ready to serve the soup, combine the basil and pine nuts with a pinch of salt in a food processor. With the processor running, add the remaining 1/4 cup olive oil in a slow, steady stream to make a smooth pesto. Just before serving, swirl the pesto into the soup, and serve with a sprinkling of grated cheese.