Cook the pasta: In a large pot, cook the shell pasta according to package instructions. Drain and set aside.

Cook the beef: In a large skillet, heat olive oil over medium heat. Add the ground beef and cook until browned, breaking it up into crumbles as it cooks. Drain any excess fat.

Sauté the aromatics: Add the diced onion and minced garlic to the skillet with the beef. Cook for 2-3 minutes until the onion is softened.

Add the creamy sauce: Stir in the cream of mushroom soup, beef broth, heavy cream, salt, pepper, and Italian seasoning. Bring the mixture to a simmer and cook for 5 minutes, stirring occasionally.

Combine the pasta and sauce: Add the cooked pasta to the skillet with the creamy beef mixture. Stir to coat the pasta evenly with the sauce.

Serve: Once everything is well combined and heated through, serve the creamy beef and shells hot. Optionally, garnish with shredded mozzarella cheese for added creaminess.