Heat 1/4 of olive oil in a soup pot and cook the onion, garlic and celery. Salt the vegetables lightly and cook until they start to soften. Add the herbs and chili flakes, then add the tomatoes, stirring to break them up as they soften. Cook about 4 minutes.
Add the chopped green and the water, cover the pot and cook over low heat until the greens are wilted.
Add the beans, broth and Parmesan rind. Bring to a simmer, then add the bread and 1/2 cup of olive oil. Cover, turn the heat as low as you can, and cook half an hour, stirring periodically. If it seems too dry when you stir it, add some more broth or water. As the bread absorbs all the liquid, it melts into the broth.
Stir in another 1/2 cup of olive oil and remove the Parmesan rind.
Serve warm, topped with grated Parmesan.