Peel the potatoes, cut them into small chunks, and cover them with cold water in a saucepan. Bring the saucepan to the boil, and then simmer the potatoes until soft (15 – 20mins).
Put the milk and fish in a saucepan / poacher. Heat the milk and simmer the fish, covered for 8 – 10 minutes. Then remove the fish with a slotted spoon and set aside. Keep the fish liquid.
Add the corn flour to the fish liquid and stir constantly with a wooden spoon over a low heat to make a sauce. Season with salt and pepper.
Once the sauce has thickened stir in the frozen peas and cook for 2 – 3 minutes.
Cover the bottom of a shallow ovenproof baking dish with the poached fish and then pour over the fish sauce with the peas in.
Drain the cooked potatoes, tip them back into their saucepan and mash together with the yogurt. Season to taste and spoon mash over the fish mixture in the dish.
Bake for about 25 – 30 mins until lightly browned. Allow to rest for 5 – 10 minutes before serving.
Notes
*For the fish pie mix, sometimes you can get pre-made up packages of mixed filling in your local supermarket. If not or just ask your fishmonger for a 340g mix of skinless, boneless haddock, salmon and smoked haddock.