Drain and rinse one can of beans, then transfer them to a blender or food processor along with 1 cup of the vegetable broth. Blend until smooth and creamy, then set aside. This blended mixture will help create a velvety texture in the soup. Drain and rinse the remaining two cans of beans and set them aside for later use.

In a large, heavy-bottomed pot, heat the olive oil over medium heat. Add the diced onion, carrots, and celery, stirring occasionally as they soften and release their natural sweetness. Sauté for about 5 minutes, or until the vegetables become tender and aromatic. Stir in the minced garlic and cook for another minute, just until fragrant.

Pour in the pureed bean mixture, followed by the whole beans and the remaining vegetable broth. Stir in the minced rosemary, dried thyme, salt, black pepper, and a pinch of crushed red pepper flakes for a hint of heat. Bring the soup to a gentle simmer and let it cook for 15 minutes, allowing the flavors to meld together.

Stir in the chopped spinach or kale, letting the greens wilt into the soup. Continue simmering for another 10 minutes until the flavors deepen. Just before serving, add the fresh lemon juice and Parmesan cheese, stirring until fully incorporated. Taste and adjust seasoning with additional salt and pepper if needed.

Ladle the soup into bowls and garnish with fresh parsley and a sprinkle of extra Parmesan cheese. Serve hot with crusty bread or warm biscuits for a hearty, comforting meal.