According to Lidia Bastianich, the queen of Italian cuisine, cavolo nero is the traditional green used in Tuscan Ribollita, a hearty vegetable soup thickened with day old bread. Ribollita is Italian for “reboiled.” Ribollita was originally peasant food, invented to stretch leftover minestrone. The soup was so delicious and satisfying, Ribollita eventually morphed into a dish in its own right.
Ribollita is a true pantry supper. It begins with soffrito, the Italian base of sautéed onions, celery, carrot, and garlic. Canned tomatoes provide depth of flavor while cannellini beans are a cheap but tasty source of protein. The blistered leaves of cavolo nero contribute texture and a nutty, slightly bitter flavor. Chunks of stale bread added at the end of cooking absorb broth, thickening the soup. This is not a long-cooking soup, but adding ingredients in stages helps to develop flavor. —la domestique
cloves garlic, thinly sliced
crushed red chili pepper flakes
rib of celery, chopped
(1 can) plum tomatoes
fresh thyme leaves
potato, peeled and diced
cavolo nero, or any other variety of kale, trimmed and chopped into bite sized pieces
(1 can) cannellini beans, rinsed and drained
thick slices of country bread, torn into pieces
Heat olive oil in a large, heavy-bottomed soup pot or Dutch oven over medium heat. Add garlic, onion, and crushed red chili pepper flakes. Sweat the onions until translucent, about 5 minutes.
Toss in the carrot and celery with a pinch of salt and sweat the vegetables 10 minutes.
Meanwhile, trim the hard stem ends off the tomatoes and discard. Crush the tomatoes with your hands.
Pour the tomatoes (and their juices) into the pot with the thyme, potato, and 3 cups water. Bring the soup to a simmer, turn the heat down and partially cover with the lid. Keep the soup at a low simmer for about 20 minutes.
Toss in the kale with another cup of water, a pinch of salt and some freshly ground pepper. Partially cover the pot and simmer for 10 minutes.
Add the canned beans and continue to simmer the soup 5 more minutes.
Stir in the bread and serve with a drizzle of spicy Tuscan extra-virgin olive oil. The soup should be thickened by the bread, but not at all dry.