1. Preheat oven to 200°C/Fan 180°C/Gas Mark 5.
2. Place the Fish in an oven-proof dish and cover with the milk. Bake in the oven uncovered for 30 minutes or until the Fish is cooked through.
3. Meanwhile, peel and chop the potatoes, and boil with a pinch of salt until soft.
4. Once the Fish is done drain the milk into a jug and put aside. Flake the fish with a fork and leave in the dish.
5. When the potatoes are done, drain, then add 30g of the butter and a splash of the reserved milk and mash together until you have a creamy texture.
6. In another saucepan melt the remaining 20g of butter on a medium heat and slowly add the flour stirring constantly until you get a smooth paste. Add the remaining milk a little bit at a time, stirring constantly, until you get a sauce-like consistency. Add the parsley and stir well. Cook for 5 minutes, constantly stirring.
7. Add the sauce to the flaked fish and mix well. Top with the mashed potato and spread evenly. Sprinkle the grated cheese even over the potato topping. Place back in the oven for 30 – 40 minutes, or until the cheese is bubbling and slightly golden brown.
8. Once cooked, remove from the oven and leave to cool for 5 to 10 minutes. Serve with fresh steamed vegetables & enjoy!