I found this recipe when I googled "Traditional Italian Christmas Dinners" this past Christmas. I had never heard of cardoons before. They are related to the artichoke and are native to Italy and other areas along the Mediterranean. The hardest part of this recipe is cleaning the cardoons! The soup itself is pretty easy to make.
1 bunch of cardoons (also called cardones), 2 to 2 1/2 pounds
3 tablespoons lemon juice
1 large onion, cut into large pieces
2 tablespoons butter
1/2 teaspoon kosher salt, divided
6 cups chicken broth
1 cup heavy cream
Add the lemon juice to a large bowl of cold water.
Clean and trim the cardoons. You need to remove the leaves along each side as well as the "strings" along the back. There are several videos on YouTube that show you the best way to clean cardoons. Cut the cardoons into 2-inch pieces, immediately putting the cut pieces into the acidulated water.
Melt the butter in a large pot over medium-high heat. Add the onion pieces and sprinkle them with 1/4 teaspoon of the kosher salt. Cook until the onions are translucent and begin to soften, about 3 to 4 minutes.
Drain the cardoons and rinse them slightly. Add the cardoons to the pan and sprinkle with the remaining 1/4 teaspoon kosher salt. Give the pan a good stir to mix everything up and then add the chicken broth. Bring to a boil over high heat. Reduce the heat to maintain a steady, lively simmer. Partially cover the pot and simmer for 1 hour, until the cardoons are very tender.
Remove the pot from the heat and, working in batches, puree the soup in a blender (I tried to use an immersion blender the first time I made the soup but ended up getting on the regular blender, which worked much better). The cardoons are very fibrous, so after each batch is pureed, pour it through a sieve into another large pot. Using a large spatula, press down on the fibrous strings to extract all the liquid and then discard the fibers. Continue pureeing and straining the soup until it is all finished. The soup can be made up until this point and stored in the refrigerator or even frozen. When ready to serve, proceed as follows.
Return the strained broth to the heat. Stir in the heavy cream and heat over medium heat just until the soup is hot (do not let it boil). Serve immediately.