To make the celeriac mash.

• Use a sharp knife to cut the outer bark off the celeriac and dice into 1 inch cubes.
• Once the celeriac is tender and cooked through, drain off and return to the pan.
• Add the butter and milk and mash the same way you would mash potatoes.

For the fish pie filling.

• Preheat the oven to 170℃ or 350℉
• Melt the butter in a medium sauce pan (if using the onion add it now, and let it sweat gently for about 5 minutes before adding the cornflour) If not using the onion, add the cornflour.
• Mix to make a thick paste and let cook for about 2 minutes.
• Slowly add the milk and scrape the bottom of the pan, loosening any brown bits.
• Bring the milk to the boil and let simmer for about 2 minutes until the mixture is thickened.
• Add the frozen peas and the fish mix. Let simmer gently for a further 5 minutes.
• Add the chopped parsley.
• Place the fish mixture into an oven proof baking dish.
• Top with the celeriac mash and some fresh pepper.
• Bake in the oven for about 20 minutes.

Makes 4 adult portions of 8 children’s portions.