Pare the potatoes and place in a pan of salted boiling water. Simmer gently for 15-20 until the potatoes are cooked. Drain, add 50g of butter and mash to smooth. Stir through 1 tbsp creme fraiche and check seasoning. Set aside till later.
In a large saucepan add 50g butter and once melted, turn to a medium heat. Add the onion, leek and carrot and cook gently for 15 minutes, taking care to soften the vegetables but not colour them. Add in the frozen peas and cook for a further 2 minutes.
Add the parsley and the double cream to the pan, stir to combine and check the seasoning. Take off the heat and set aside till later.
Place the fish pieces on the bottom of a large oven-proof dish.
Pour the creamy vegetable sauce over the top of the fish, taking care to cover the entire dish.
Carefully spoon over the mashed potato and spread it across the fish and sauce. Use a fork to gently push the potato into all corners of the dish, ensuring you cover the fish completely.
Place in a pre-heated oven at 180CFan for 35-40 minutes. Once cooked serve immediately.
In this dish we have used haddock, but this could have been easily substituted with cod or colley. Salmon can be used as a substitute for smoked haddock. If you like prawns then add a handful to the mix. Cook the fish that you like to eat.