In a large bowl, combine the sausage, beef, onion, breadcrumbs, heavy cream, parsley, cheese, garlic, salt, Italian seasoning, pepper, red pepper flakes, egg. Do not add the beef broth.
½ pound ground Italian sausage, ½ pound ground beef, ½ cup white onion, ¼ cup breadcrumbs, ¼ cup heavy cream, ¼ cup parsley, ¼ cup Parmesan cheese, 2 garlic cloves, 1 teaspoon salt, 1 teaspoon Italian seasoning, ½ teaspoon ground black pepper, ¼ teaspoon red pepper flakes, 1 large egg