Pre-heat the oven to 200ºC
Place the potatoes in a pan with enough water to cover, add a pinch of salt and bring to the boil. Cook for 15-20 minutes until they are soft. Spray a frying pan with low calorie cooking spray and fry the leeks and onions for 2-3 minutes, until soft.
Add the chicken and bacon and cook for 5 minutes, then add mustard powder. Add the stock cube to the boiling water and add 300ml of the chicken stock to the pan. Bring to a simmer and cook for 10 minutes.
Add 75g of the cream cheese and the thyme to the chicken. Stir until completely mixed, then transfer to the ovenproof dish.
When potatoes are cooked, drain and leave for a few minutes then mash until smooth.
Add 25g of cream cheese, parsley and the remainder of the chicken stock to the mashed potatoes and mix. Season to taste with salt and black pepper.
Spoon the potato over the chicken mix and level using the back of a fork. Sprinkle with the grated cheese and cook in the oven for 25-30 minutes until golden brown.