1. Preheat your oven to 200°C

Mash Potato

1. Add your potatoes to a saucepan of cold water. Bring to the boil and cook until tender.

2. Drain your potatoes and add in your butter, cheese, salt and pepper. Mash until it reaches your desired texture.

Fish Sauce

1. Whilst your potatoes are cooking, in another saucepan melt your butter.

2. Once melted, add your flour and mix to form a roux. Cook the roux for 2 minutes.

3. Add your warmed milk to your roux in small amount, mixing in thoroughly at each addition. Only add more milk when the last addition has started to boil.

4. Once you have added your milk and the mixture is thick, add in salt, pepper, parsley and mustard.

5. Pour the mixture into your pie dish and add the fish, stir this through. Add clingfilm to the top of your mixture to prevent a skin forming whilst waiting for your mash to be ready.

6. Spoon your mash onto the top of your pie and smooth to cover all the mixture. Add texture to the top of your mash using a fork to promote crispy bits.

7. Bake for 30-35 minutes in the oven until the mash is golden brown.