If you plan to serve this Tuscan ribollita in the traditional sense, over several days, only use the portion of toasted bread appropriate to the number of servings. Store the rest in an airtight container at room temperature to add to remaining soup.
kosher salt and freshly ground black pepperto taste
Preheat oven to 350°F.
Place torn bread on rimmed baking sheet in a single layer. Drizzle with 3 tablespoons olive oil and toss with your hands to coat. Bake until golden brown, tossing a couple of times, about 15 minutes. Set aside to cool.
Meanwhile, heat 1 tablespoon olive oil in a large soup pot or Dutch oven over medium heat. Add onion, carrot, and celery; cook and stir until onion is translucent, about 5 minutes. Add garlic, sausage and white wine; cook and stir until sausage has cooked through. Add kale, tomatoes, beans, and broth; bring to boil. Reduce heat and simmer 30 minutes, stirring occasionally. Season to taste with salt and pepper.
Divide croutons among 6 bowls and ladle soup over. Serve topped with Parmesan shavings and drizzled with olive oil.
If you prefer a milder soup, use sweet Italian sausage and add red pepper flakes to taste when you add the garlic, sausage and white wine in step 3.
For a vegetarian version, skip the sausage and use vegetable broth.