Bring a large pot of salted water to a boil. Add the pasta and cook according to package directions. Reserve 1/2 cup cooking water, then drain.
While the pasta is cooking, season the chicken with salt, pepper and Italian seasoning. Add the flour and toss to coat.
Heat the oil in a large skillet over medium-high heat. Add the chicken and cook, stirring occasionally, for about 5-7 minutes or until browned, Add extra oil, if needed. Remove from the skillet and reserve.
To the same skillet, add the butter and saute the onions for about 3 - 4 minutes or until they become translucent. Add the garlic and cook for a minute.
Deglaze the skillet by adding the chicken broth. Scrape the bottom of the pan to remove the brown bits. Bring to a boil. Stir in the pesto and lower the heat. Add the half and half and garlic powder. Simmer for about 2-3 minutes.
Return the chicken and any collected juices to the skillet and toss to coat. Simmer for 3-4 minutes. Stir in the Parmesan cheese and mix well.
Add the cooked pasta and toss gently. Add some of the cooking water only if a creamier consistency is desired. Serve warm garnished with chopped basil (optional).
Notes
When cooking this creamy pasta recipe, make sure the sauce doesn't boil as it can separate.
Pasta dishes are best served immediately after tossing the pasta with the sauce. If you wait too long to serve it, the pasta tends to dry up.
If your pasta gets too dry, add additional pasta cooking water to make the pasta creamier again.