1. In a medium bowl, combine sausage, rice, mozzarella and basil. Spoon mixture into peppers, filling each one about 3/4 full. Place peppers in slow cooker. Pour tomatoes over peppers. Pour broth around sides of peppers.
2. Cover and cook on low until peppers are softened, rice is tender and filling is cooked through (an instant-read thermometer stuck into filling should read 165ºF), 5 to 6 hours. Sprinkle peppers with Parmesan and serve.