Cook the pasta according to the packet instructions, then drain.
Spray a frying pan with low-calorie cooking spray. Add the chicken and onions and fry until the chicken has browned and onions are softening. Add the mushrooms and cook for a few more minutes.
Sprinkle over the sachet and mix for 2 minutes, until the chicken and veg are equally coated and cooked thoroughly.
Add the water, stir and simmer for 10 minutes until reduced. Add the cream cheese, pasta, and peas. Stir to combine, until the peas are heated through.