A Smoked Fish Supper

I love smoked food of all kinds, in particular smoked fish. I remember the bright yellow smoked haddock from my childhood and while today's undyed version looks less garish but tastes as good. This recipe is based on one of my favourites from Loch Fyne and works as well with cod or haddock.
Serves 2

Ingredients
1 thick fillet of smoked haddock or cod (divided into two portions)
1/2 pint milk
Large knob of butter
Teaspoon of grain mustard
small bunch of parsley finely chopped (reserve the stalks)
3 fist sized potatoes
100g frozen peas

Boil the potatoes and poach the fish in the milk with the parsley stalks until the fish is just done (about 10 minutes). Keep the fish somewhere warm (and away from hungry cats!). Mash the potatoes with some of the strained poaching milk, most of the butter and half the chopped parsley. Cook the peas. Add the rest of the butter, parsley and mustard to the remaining milk and then add the cooked peas.
Put the mashed potato in the bottom of a shallow bowl, place the fish on top and them pour over the pea sauce mixture.