Wash, peel then dice Potatoes. Cook in boiling water, (or steam), for about 15 minutes until just cooked, then put to one side
Wash the leeks, remove the dark tops, then slice thinly into an oven- proof dish.
Wash fish under a tap, do not dry. Remove any bones. Wrap in greaseproof paper and microwave for just three minutes. Flake apart with a fork and add to the dish.
Add Peas and Sweetcorn if using
Put the flour into a medium saucepan, start to heat. Add the milk gradually, stirring to prevent lumps.
Add crumbled stock cubes and butter, stir to mix. Bring to the boil, then turn down to a simmer, stirring all the time, until the sauce thickens.
Pour sauce over contents of the dish, making sure everything is covered all the way to the edges.
Mash Potatoes, with a little butter and milk, to a creamy consistency. Spread over contents of dish, mark with a fork. Sprinkle over evenly the Parmesan Cheese.
Heat in a medium oven, gas mark 6, 220F, for about 15-20 minutes until golden brown and smells very Cheesy!!
