Cook the pasta shells according to the package instructions in a large pot of salted boiling water until just al dente. Drain and set aside.
Brown the Beef:
While the pasta is cooking, heat the olive oil in a large skillet over medium-high heat. Add the ground beef and cook until browned, breaking it up with a spoon as it cooks. Drain any excess fat.
Add the chopped onion to the skillet with the beef. Cook until the onion is softened, about 3-4 minutes. Add the minced garlic, Italian seasoning, salt, and pepper, and cook for another minute until fragrant.
Add Tomato Sauce and Broth:
Stir in the tomato sauce and beef broth. Bring the mixture to a simmer, reduce the heat to low, and let it simmer for about 10 minutes to combine the flavors.
Make It Creamy:
Stir in the heavy cream and bring the mixture back to a simmer. Cook for a few more minutes until the sauce thickens slightly.
Combine Pasta and Beef Mixture:
Add the cooked pasta shells to the skillet and stir until they are well coated with the sauce.
Add Cheese:
Sprinkle the shredded cheddar cheese over the pasta and beef mixture. Cover the skillet with a lid or aluminum foil and let it sit off the heat until the cheese is melted, about 2-3 minutes.
Garnish and Serve:
Garnish with chopped fresh parsley before serving.