Heat the olive oil in a large pot over medium heat. Add the diced onion and cook for 3 minutes until it softens. Stir in the minced garlic and cook for 1 minute more.
Add the sausage to the pot. Break it up with a spoon and cook until browned, about 6 minutes.
Stir in the drained cannellini beans, diced tomatoes, chicken broth, and dried rosemary. Bring the mixture to a simmer.
Reduce the heat to low and let the stew cook for 15 minutes, stirring now and then.
Add the chopped kale and stir until it wilts, about 3 minutes. Season with salt and black pepper to taste.
Ladle the stew into bowls and top each serving with grated Parmesan cheese.