In a large pot, heat the olive oil over medium heat. Add the onion, garlic, carrot, and celery, and cook until the vegetables are softened, about 5 minutes.
Stir in the dried thyme and bay leaf, cooking for another minute until fragrant. Add the vegetable broth and bring the mixture to a boil.
Reduce the heat to low and add the white beans. Simmer for about 20 minutes, allowing the flavors to meld.
Stir in the chopped kale and continue to simmer until the kale is tender and bright green, about 5-10 minutes.
Remove the bay leaf. Season the soup with salt and pepper to taste. Serve hot, with a sprinkle of grated Parmesan cheese and a squeeze of fresh lemon juice if desired.