Bring a large pot of salted water to a rolling boil. Add the pasta shells and cook for 8-9 minutes until al dente. They should still have a slight bite since they'll continue cooking when mixed with the sauce. Drain in a colander and set aside.

While the pasta cooks, heat a large skillet over medium heat. Add the ground beef, chopped onion, and minced garlic. Break up the beef with a spatula and cook for 6-7 minutes until the meat is browned and no pink remains. The onions should be soft and translucent. Drain any excess fat from the pan.

Pour in the beef broth and sprinkle in the Italian seasoning. Stir everything together and let it simmer for 5 minutes. The liquid will reduce slightly and the flavors will intensify.

Reduce the heat to low and stir in the heavy cream. Let the sauce simmer gently for another 5 minutes, stirring occasionally. The sauce will thicken and coat the back of your spoon when ready. Avoid boiling to prevent cream separation.

Add the cooked pasta shells to the skillet and gently fold them into the sauce until every shell is coated. Taste and adjust the seasoning with additional salt and pepper if needed. Serve immediately while hot, garnished with Italian seasoning or fresh herbs.