1. In your largest thick-bottomed pot over medium heat combine the olive oil, celery, garlic, carrot and onion. Cook for 10 to 15 minutes, stirring to soften the vegetables but avoid any browning. Stir in the tomatoes, potatoes, zucchini, peas and red pepper flakes, and simmer for another 10 minutes or so. Stir in the kale, 3 cups of the beans and 8 cups water or broth and meat, if using. Bring to a boil, reduce the heat, and simmer until the greens are tender, about 15 minutes.
2. In the meantime, mash or purée the remaining beans with a generous splash of water — until smooth. Tear the bread into bite-sized chunks. Stir both the beans and bread into the soup. Simmer, stirring occasionally, until the bread breaks down and the soup thickens, 20 to 30 minutes. Stir in the salt, taste and add more if needed. Stir in the lemon zest and/or parsley if using.
3. Serve immediately, or cool and refrigerate overnight. Finish each serving with a drizzle of olive oil and some chopped olives or basil pesto.

There are about as many versions of this soup as there are Italians, but it always has kale and beans. Tuscan kale is traditional for this dish, and it has become quite easy to find in our area the past few years, particularly at farmers’ markets. But I have used common curly kale and that works just fine. I used my own dried beans from the garden, but canned cannellini or Great Northern beans are the usual base. is is often a vegetarian dish, but you can also throw in a ham bone if you have one leftover from holiday eating, or put in a little bacon or Italian sausage.

One of my most favorite things about soup is how forgiving it is: Use up leftovers in this and substitute vegetables as your pantry is stocked. If you’ve got a few spoonfuls of leftover mashed potatoes, definitely throw them in! If you don’t have a zucchini on hand, don’t run to the store just to get one; you can leave it out. If you’ve got basil pesto on hand, you can add a dollop to the bowl at serving time. is makes a really big pot — enough for a dinner party. Leftovers freeze really well.