I have no hesitation using canned beans in soups. Napolina cannellini beans are brilliant, and cheap. Mentioning using kale in soup reminded me of one of the best of all Italian soups, ribollita. A fantastic soup for anyone, including veggies. I start with chunky soffritto: chopped carrots, onions and celery in olive oil. When the veg is soft I chuck in canned tomatoes, some sundried tomato paste, a bit of white wine, veg stock and beans. Tons of beans. And seasoning, of course. After a bit of simmering I throw in an impossibly large amount of chopped cavolo nero and let it cook for about ten minutes. What you do next is crucial: you need some ciabatta or other crusty white bread, which you toast then rub with very garlicky olive oil. Put the bread into bowls and ladle the soup on top. You'll live forever.

All the better if you make the ribollita the day before. Ribollita means "reboiled".