Peel and chop the potatoes and boil until tender. Drain & mash with the butter, cream & seasoning.
To make the sauce, melt the butter, add the flour & cook gently for 2 minutes until thickened. Gradually whisk in the milk & bring to the boil, stirring continuously until sauce has thickened. Add the cheese, cream, mustard, nutmeg, seasoning & parsley. Cook for a further minute whisking all the time.
Pour enough sauce to cover the base of an oven proof dish. Add the fish pie mix, followed by the eggs, peas & spinach. Cover with the remaining sauce, top with the mash & sprinkle with cheddar cheese.
Bake in the centre of the oven for 40 - 45 minutes.