In a large saucepan over medium heat, saute pancetta or bacon until browned and some fat has rendered out, about 2 minutes. Remove meat from pan and set aside. Add garlic, thyme, or sage, black pepper and chili flakes, heat 30 seconds.
Place broth in pan, bring to a boil, reduce heat, and simmer covered for 10 minutes. Stir in pancetta or bacon, kale and 1 cup beans; simmer for 10 minutes. Carefully puree soup in a blender, return to pan and stir in remaining beans and lemon juice. If soup is too thick, stir in additional broth or water.
Serve topped with Parmesan and freshly ground black pepper.