Bring a large pot of salted water to a boil and cook the penne pasta until al dente. Reserve 1–2 cups of pasta water, then drain.
Heat olive oil and butter in a large pan over medium-high heat. Add chicken and cook for 6–7 minutes until golden. Remove and set aside.
In the same pan, sauté garlic for 1 minute. Add chicken stock and bring to a boil.
Stir in flour and whisk until smooth and creamy.
Pour in the half and half, whisking continuously to avoid lumps. Simmer for 2–3 minutes until slightly thickened.
Add Italian seasoning, chili flakes, and black pepper.
Stir in cheddar cheese until melted and the sauce becomes creamy.
Add cooked pasta and toss well to coat. Use reserved pasta water if needed.
Return chicken to the pan, mix well, then stir in Parmesan cheese.
Adjust seasoning and serve immediately. This cheesy chicken pasta is best enjoyed fresh.