When you say you have bought fish pieces do you mean fillets, if fillets is the skin on or off, or have you bought cubed fish pie mix?
What kind of fish pie do you like, a potato or pastry topping? Do you like a cheesy sauce or a parsley one in the filling? Do you know how to make a white sauce based on a roux?
How much fish have you bought and how many portions of pie are you hoping to make?
I'll try to help but am quite busy this afternoon but will try to help.
Are you sure you've never made a basic white sauce with melted butter and flour mixed to combine and then slowly adding milk and whisking 'til smooth? Much nicer than a packet!
Fish pie is very easy .
Poach the fish in some milk .Remove fish from milk .Using equal amounts of flour and butter to make a roux .Add the mik you poached the fish in and some fresh chopped parsley,season and stir until smooth and thickish Gently mix the fish into the sauce .Shove it in a dish and let it cool a bit. Dollop mash over and sprinkle with breadcrumbs or grated cheese Brown in oven .
i made the roux when I was at school many years ago - haven't a baldy - can't remember - just something start of with a wee ball of flour and milk or something - that is my limit LOL - Eccles when you get yourself sorted and get it written I will copy and paste and print. Thanks again. God yous are all great cooks.
Conne...
measure out equal amounts of flour and butter
melt butter and add flour and stir with a whisk over a low heat for a few mins to cook out the taste of flour
add the poaching milk (let it go cool) bit by bit.
it will appear to go lumpy but as long as you keep stirring the lumps will go.
keep adding the milk until you have the desired consistency.
Season and add your chopped parsley or cheese.
If you are using a packet of parsley sauce....poach your fish in the amount of milk the packet instructs to use and when fish is poached use the milk and follow the packet instructions.
put fish in baking dish, tip over sauce and top with mash.
Can I suggest, since conne and I seem to be of the same school of cooking (i.e. not much) - conne, go and buy a ready made fish pie sauce. Morrisons do one here, it's delicious. I cook the fish, pour the sauce over, then put the potato on top. Fairly foolproof, even I can do it :-)