Empty the contents of the cheese sauce sachet into a jug, fill to 400 ml with boiling water and stir for 1 min.
Cube the butternut and microwave in a little water on high for 7 min.
In a large pan, brown the onion and chicken breasts in oil.
Add the sachet of seasoning mix, 600 ml hot water, butternut and pasta to the chicken.
Bring to the boil, stirring occasionally.
Reduce heat and simmer for 10 min.
Pour into a 2-litre oven dish.
Pour cheese sauce over and sprinkle with crumbled feta cheese.
Grill for 10 min or bake for 20 min at 180°C.