Pour the vegetable oil into a large skillet and place over medium-high heat.
Once the pan is hot, add the chicken pieces and diced onion. Saute until the onions are softened and the chicken is browned on all sides.
Add the garlic, broth, water and pasta; stir.
Bring to a boil and let the mixture boil for 15 minutes, stirring occasionally.
Add the pesto and cream cheese and stir until the cream cheese is melted.
If you'd like to thicken the sauce a bit, continue to cook over low heat for a couple minutes. If you want to add more liquid, simply add a splash of chicken broth and stir it in.