Heat your oven to 200°c/180°c fan/gas mark 6.
Peel and cut the potatoes into quarters then put them into a saucepan. Cover them with cold water and put the pan over medium heat. When the water is boiling, turn down the heat to a simmer and let the potatoes cook!
- 100 g butter
- 200 ml semi-skimmed milk
Drain the potatoes in a colander, then put them back into the pan and mash them with a potato masher. Add the butter and milk to the pan and mash again until the potatoes are nice and smooth.
- 4 tbsp fresh parsley
- 4 spring onions
While the mash is cooking, slice the spring onions into small rings. Then chop the parsley with a large knife or in a mug with a pair of scissors.
Grate the Cheddar cheese.
Place the casserole dish over medium heat and add the butter. When the butter has melted, add the spring onions and fry for a minute.
- 175 g frozen peas
- 1 tsp Dijon mustard
Add the peas and mustard and cook for another minute, stirring.
- 150 ml semi-skimmed milk
- 200 ml double cream
Add the milk and double cream and gently simmer for 5 to 10 minutes. Then add the cheese and give it a good stir!
When the cheese has melted, add the fish and cover them with sauce. Stir in the chopped parsley and remove from the heat. Stir again.
Spoon the mash on top of the fish mixture and spread it out. Use a fork to make a wavy pattern like the sea.
Put the dish into the oven and cook for 20 to 26 minutes.