Heat a 12 inch skillet over medium heat and add the butter to melt. Stir to coat the pan.
Add the chicken to the skillet and sprinkle with salt and pepper. Cook, stirring often, until the chicken is browned, about 5 minutes.
Add the onion to the pan and cook 2 more minutes, stirring often.
Add the pasta and sun-dried tomatoes to the skillet. Pour in the broth and half and half. Stir well to combine.
Bring to a boil, cover, and reduce to a simmer.
Cook for 12 minutes or until pasta is tender.
Remove the lid and stir in the grated cheese until melted.
Stir in the spinach. Remove from heat, cover, and let sit for 5 minutes to wilt spinach.
Stir well before serving.