Bring a large pot of generously salted water to a boil. Cook the linguine according to package directions until al dente. Drain and set aside. If the pasta finishes before the sauce, toss with a drizzle of olive oil to prevent sticking.

While the pasta cooks, place the flour in a shallow dish. In a small bowl, whisk together 1/2 teaspoon of the salt, the black pepper, garlic powder, smoked paprika, and cayenne (if using).

Sprinkle the chicken breasts evenly with the spice mixture, rubbing it into the meat. Lightly dredge each breast in the flour, shaking off any excess.

Heat the olive oil and butter in a large skillet over medium-high heat. When the butter is melted and shimmering, add the chicken breasts, spacing them apart. Cook until golden brown, about 2-3 minutes per side, and the chicken is cooked through (165°F internal temperature). Transfer to a plate and set aside.

Reduce the heat to medium. Add the chopped onion to the skillet and cook, stirring occasionally, until softened and translucent, about 5 minutes.

Add the minced garlic and cook until fragrant, about 30 seconds.

Slowly pour in the chicken broth while scraping up any browned bits from the bottom of the pan. Stir in the heavy cream, the remaining 1/4 teaspoon salt, and the Italian seasoning.

Bring the sauce to a gentle simmer. Add the Parmesan cheese and stir until melted and smooth. Taste and adjust seasoning with additional salt and pepper if needed.

Add the cooked linguine to the skillet. Slice the chicken into strips or leave whole, then return it to the pan. Toss everything together and simmer for 1-2 minutes until the chicken is warmed through and the sauce coats the noodles. Garnish with fresh parsley and serve immediately.