Meanwhile, in a large skillet, add olive oil & saute onions for about 5 minutes over medium heat. Turn the heat to high, then add chicken and mushrooms; brown for approximately 5 more minutes.
Add vodka and reduce completely. Stir in cream and tomato sauce, then bring to a simmer. Season with salt and pepper.
Cook pasta according to directions. Drain and toss with sauce, then stir in cheese and parsley right before serving.