Set a medium pot over medium-high heat, add a good glug of olive oil and saute the onion, celery and carrots for 5-7 minutes, until soft. Add the garlic and some salt and pepper and cook for another minute or two.
Add the stock, tomatoes, beans, potato, rosemary and/or thyme and bring to a simmer; cook for about 10 minutes, until the vegetables are tender. Pluck out the herb stems and stir in the kale. It will only need a couple minutes to wilt.
There are a few ways to do the toast: cut thick slices, toast them, then set a piece in the bottom of each bowl, drizzle with good olive oil, ladle the soup over top and grate Parmesan over the whole thing. Or run the bread, topped with grated cheese (and oil too if you like) under the broiler, and set a piece atop each bowl of soup. Or ladle the soup into ovenproof dishes and top with bread and cheese a la French onion soup, place the bowls on a baking sheet and run the whole lot under the broiler.