Begin by cooking the pasta shells according to the package instructions in a large pot of boiling salted water. Drain well and set aside.

In a large skillet, heat the olive oil over medium-high heat. Add the ground beef and cook for 3-5 minutes, breaking it up until browned. Drain any excess fat and set the beef aside.

Using the same skillet, add the diced onion. Sauté for about 2 minutes until the onion starts to get translucent, then add the minced garlic and cook for an additional minute.

Whisk the all-purpose flour into the skillet with the onions and garlic, cooking for about 1 minute until lightly browned.

Gradually whisk in the beef stock, then add the marinara sauce along with the Italian seasoning, dried parsley, oregano, and smoked paprika. Bring to a boil.

Reduce heat and let it simmer for about 6-8 minutes, stirring occasionally until the sauce thickens slightly.

Stir in the cooked pasta and return the browned beef to the skillet. Mix until the pasta is well-coated with the sauce.

Pour in the heavy cream, stirring until heated through, about 1-2 minutes. Adjust seasoning with salt and pepper.

Finally, stir in the sour cream and fold in the freshly grated cheddar cheese, allowing it to melt completely.

Serve immediately, garnished with a sprinkle of fresh parsley if desired.