In a large skillet or Dutch oven, cook ground beef and chopped onion over medium-high heat for 5–7 minutes, breaking up meat as it browns. Cook until beef is done and onion is softened. Drain any excess fat.

Stir in ranch seasoning and pour in beef broth. Mix well, scraping any browned bits from the pan bottom.

Add pasta shells. Bring mixture to a boil, then reduce heat to low. Cover and simmer for 10–12 minutes, stirring occasionally, until pasta is al dente and most of the liquid is absorbed.

Add shredded cheddar cheese and stir for 1–2 minutes, until cheese is melted and sauce is creamy.

Season with salt and pepper to taste. Serve hot, optionally garnished with extra cheese, parsley, or chives.