Pat the chicken strips dry and season all over with the salt, pepper, and Italian seasoning. Heat the olive oil in a large, deep skillet or Dutch oven over medium-high heat. Sear the chicken in a single layer for 5–6 minutes, turning once, until golden at the edges and cooked through (165°F / 74°C internal temperature). Transfer to a plate and set aside.

Reduce the heat to medium. Melt the butter in the same pan, scraping up the browned bits. Add the minced garlic, Italian seasoning, and red pepper flakes (if using) and cook for 30–60 seconds, stirring constantly, until fragrant — don't let the garlic brown or it turns bitter.

Pour in the chicken broth, scraping the bottom of the pan to release every flavorful bit. Stir in the heavy cream and bring to a gentle simmer — not a hard boil. Add the uncooked penne, stir well, then simmer for 10–12 minutes, stirring occasionally, until the pasta is al dente and most of the liquid has become a creamy sauce.

Reduce the heat to low. Sprinkle in the grated parmesan a handful at a time, stirring until each addition melts before adding more — this keeps the sauce silky instead of grainy. Return the seared chicken (plus any accumulated juices) to the pan along with half the parsley and toss for 1–2 minutes until everything is glossy and coated. Taste and season with salt and black pepper.

Spoon into warm bowls, scatter over the remaining parsley and extra parmesan, and serve immediately while the sauce is hot and silky.