Add the beef broth, Worcestershire sauce, pasta, sliced steak, bell peppers, and onions to the slow cooker. Stir to combine.
Stir in the milk, mozzarella cheese, sour cream, garlic powder, paprika, and Italian seasoning. Make sure the pasta is mostly submerged in the liquid for even cooking.
Cover and cook on LOW for 4–6 hours, checking around the 3–4 hour mark to prevent overcooking. If the pasta absorbs too much liquid, add a splash of beef broth or milk.
Once the pasta is tender and the cheese has melted into a rich, creamy sauce, season with salt and pepper to taste.
Ser warm, and garnish with grated parmesan and fresh parsley, if desired. Enjoy!