Add the Italian sausage and break it up with a spoon. Once the sausage is browned and no longer pink, add the chopped onion, minced garlic, dried basil, and dried thyme.
Transfer the meat-onion mixture to a 6-quart slow cooker. Add the chopped potatoes, chicken broth, water, salt, pepper, granulated sugar, and nutmeg. Stir gently to combine.
Cover and cook on HIGH for an additional 30 minutes, until the kale is wilted and tender. Serve hot with a sprinkle of freshly grated Parmesan cheese if desired.