Heat butter and olive oil in a large deep skillet over medium heat. Add chicken, season lightly with salt and pepper, and cook for 4–5 minutes until lightly golden and cooked through.
Add garlic and cook for 30 seconds, just until fragrant.
Stir in uncooked penne and pour in chicken broth. Bring to a gentle simmer.
Reduce heat to medium-low and cook, stirring occasionally, for 10–12 minutes, until the pasta is al dente and most of the liquid is absorbed.
Stir in heavy cream, Parmesan cheese, Italian seasoning, parsley, and red pepper flakes if using. Mix until the sauce is creamy and coats the pasta evenly.
Simmer gently for 2–3 minutes, then remove from heat. Use reserved pasta water if needed to loosen the sauce.
Taste and adjust seasoning. Garnish with fresh herbs and serve warm.