Cook the Pasta:
In a large pot of salted boiling water, cook the penne according to package directions until al dente. Drain and return the pasta to the pot.
Cook the Chicken:
Season the chicken breasts with kosher salt, freshly ground black pepper, garlic powder, and Italian seasoning.
In a large skillet over medium-high heat, heat the oil, then cook the chicken until browned on both sides and cooked through.
Dice the chicken, set it aside, and cover to keep warm.
Make the Sauce:
Wipe the skillet clean, then melt the butter over medium-high heat. Stir in the minced garlic and cook for 1 to 2 minutes until fragrant.
Sprinkle the flour over the butter and garlic, stirring until it thickens.
Gradually whisk in the heavy cream until a smooth sauce forms. Season with salt and pepper, then stir in the Parmesan until melted and incorporated.
Combine and Serve:
Stir the cooked chicken and penne into the sauce, ensuring everything is well coated.
Top with additional freshly ground black pepper, fresh thyme or parsley, and more grated Parmesan. Serve immediately.