Instructions

1. Preheat oven to 180°C.
2. Peel the potatoes, cut into chunks and put into a pan of lightly salted cold water over a high heat.
3. Grease an oven dish with the oil and place into it the fish & milk.
4. When the potatoes come to the boil, turn down to a simmer; put the fish into the oven.
5. After 20 minutes drain the potatoes and take the fish dish from the oven. Turn the oven up to 210°C.
6. Mash the potatoes with the milk from the fish dish, the butter and the seasoning.
7. Mix the peas in with the mash then spread it fairly evenly over the fish, covering it to the sides of the dish.
8. Grate the cheese all over the mash then return to the oven until golden brown - about 20 minutes.