Begin by bringing a large pot of salted water to a rolling boil over high heat. Add the shell pasta and cook according to package instructions until al dente, usually about 8-10 minutes. Once done, drain the pasta in a colander and set aside, reserving a splash of the cooking water.

In a large skillet, heat a tablespoon of olive oil over medium heat. Add the ground beef, breaking it up with a wooden spoon. Sauté for about 5-7 minutes until it's browned and no longer pink. Toss in the chopped onions and minced garlic, stirring occasionally until the onions become translucent, about 3-4 minutes.

Pour in the beef broth, stirring to combine with the beef mixture. Add the Italian seasoning and let the mixture simmer for 5 minutes over medium-low heat.

Reduce the heat to low and gradually stir in the heavy cream, mixing thoroughly. Let it simmer gently for another 5 minutes until the sauce thickens.

Gently fold in the cooked shell pasta, ensuring each piece is well-coated with the creamy beef sauce. If the mixture seems thick, add a splash of the reserved pasta water.

Spoon the Creamy Beef and Shells into bowls, garnishing with extra Italian seasoning or freshly grated cheese if desired. Serve immediately.