1. Cook the Pasta: Bring a large pot of salted water to a boil. Add the medium shell pasta and cook according to package instructions until al dente. Drain and set aside.

2. Brown the Beef: In a large skillet or Dutch oven, heat the olive oil over medium heat. Add the ground beef and cook, breaking it up with a wooden spoon, until browned and cooked through. Drain any excess fat.

3. Sauté the Aromatics: Add the diced onion and minced garlic to the skillet with the cooked beef. Sauté for 2-3 minutes, until the onion is softened and the garlic is fragrant.

4. Season and Thicken: Stir in the Italian seasoning and all-purpose flour. Cook for 1 minute to eliminate the raw flour taste.

5. Add Liquids: Gradually pour in the beef broth and tomato sauce, stirring constantly to prevent lumps. Bring the mixture to a simmer and let it cook for 6-8 minutes, until slightly thickened.

6. Finish the Sauce: Stir in the heavy cream and season with salt and freshly ground black pepper to taste.

7. Combine and Serve: Add the cooked pasta shells and shredded cheddar cheese to the skillet. Stir until the cheese is melted and everything is well combined. Serve hot and enjoy!