Brown the ground beef in a large skillet with high sides along with the onion, over medium-high heat. Cook the beef, breaking it up with a spoon, until no longer pink. Drain off any excess fat and return skillet to the stove top.
Stir in the garlic and Italian seasoning, cook until fragrant, about 30 seconds. Pour in the beef broth, milk and pasta sauce, bring the mixture to a boil.
Add in the uncooked pasta shells and stir often, uncovered, until the pasta has absorbed the majority of the liquid and the noodles are tender. This should take about 15 to 18 minutes.
Stir in the shredded cheese and mix until it's well incorporated with the sauce. Season with salt and pepper to taste. Enjoy!