In a large, deep skillet heat oil over medium heat. Once hot, add chicken and cook for 5-6 minutes or until no longer pink.
Add mushrooms and cook for 3-4 minutes or until softened, stirring often. Add garlic; cook until fragrant, stirring constantly, about 30-60 seconds.
Add pasta, water, salt, and pepper. Bring to a boil and cook until pasta is tender, about 10 to 13 minutes.
When water is nearly absorbed, stir in the pesto, spinach, and half and half. Cook for 1-2 minutes until spinach is tender and wilted. Stir in Parmesan and serve hot.