1) Heat the oil in a large pot. Add the garlic and oregano and cook for no more than a minute. Add the tomato puree and vinegar, and cook for another minute.
2) Add the beans and stock and bring to a simmer. Season with salt and pepper. Add the kale and simmer, partially covered, for 1 hour. Season, to taste, again with salt and pepper before serving.
For the garlic-olive oil crostini:
1) Slice the baguette on a heavy angle to create long slices. Toast the slices in a toaster or in the conventional oven.
2) Rub them once or twice with half a garlic clove. Season a shallow plate of extra virgin olive oil with some salt and dip each side of the bread into the oil. Serve as accompaniment to the soup.