Add half of the beans to the food processor and pulse until smooth. If you need to, you can use some of the broth from the recipe to make it a smoother texture. Set aside.
In a medium pot, set over medium heat, add the olive oil. When the oil is warm, add the onion, celery and carrots. Cook for 5 to 7 minutes, until very softened softened. Mix in the garlic, along with the crushed salt, a few rounds of black pepper, red pepper, salt and thyme; cook until fragrant, about 1 to 2 minutes.
Add in the tomato paste and mix until the paste turns a deep brick red color, about 2 minutes. Mix in the reserved Parmesan-Reggiano rind, bean puree, beans, stock and kale. Reduce the heat to low, cover the pot and cook for 15 to 20 minutes, until the soup’s flavors merry.
Meanwhile, tear up half of the baguette and place on top of the soup in the pot. Top with a grating of parmesan and divide the soup amongst bowls. Garnish with a drizzle of olive oil and more parmesan, if you like.
This soup is great heating up. Store in an airtight container and will last up to 3 to 4 days in the fridge.