Cook the pasta shells according to package instructions until al dente. Drain and set aside.
In a large skillet, heat olive oil over medium heat. Add diced onion and minced garlic, sauté until softened.
Add ground beef to the skillet, cooking until browned. Drain excess fat if necessary.
Stir in Italian seasoning, dried parsley, oregano, and smoked paprika. Cook for another minute.
Sprinkle flour over the mixture, stirring to combine. Gradually add beef stock, marinara sauce, heavy cream, and sour cream.
Bring to a simmer and cook until the sauce thickens. Stir in cooked pasta shells and cheddar cheese until melted.
Season with salt and pepper to taste. Serve warm.