Bring a large pot of generously salted water to a boil. Cook the pasta shells according to the package directions until al dente. Drain well and set aside.

Meanwhile, heat the olive oil in a large skillet over medium-high heat. Add the ground beef and cook for 3–5 minutes, breaking it into small crumbles as it browns.

Once the beef is completely cooked, drain any excess fat and transfer the beef to a plate.

Reduce the heat to medium. Add the diced onion to the same skillet and cook for about 2 minutes, stirring frequently, until it begins to soften.

Add the minced garlic and cook for about 30–60 seconds, just until fragrant.

Sprinkle the flour over the onions and garlic. Stir continuously for about 1 minute to remove the raw flour taste.

Gradually pour in the beef stock while whisking or stirring to prevent lumps.

Add the marinara sauce, Italian seasoning, parsley, oregano, and smoked paprika. Stir well.

Bring the sauce to a gentle boil, then reduce the heat and simmer for 6–8 minutes, stirring occasionally, until slightly thickened.

Return the cooked beef to the skillet and add the drained pasta shells. Stir until everything is coated.

Pour in the heavy cream and gently stir. Cook for another 1–2 minutes, until the Creamy Beef and Shells Recipe is hot throughout.

Reduce the heat to low and stir in the sour cream.

Add the freshly grated cheddar and stir gently for 1–2 minutes, until completely melted and the sauce is smooth and creamy.

Season with salt and freshly ground black pepper to taste. Garnish with parsley and serve immediately.