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).