Method

1. Heat oven to 190C/170C fan/gas 5. Put the milk in a saucepan with the bay leaf, garlic and onion. Add the fish and poach on a medium heat for 15 mins. The milk should be just covering the fish, if not, add a little more.

2. Cut the potatoes and parsnips into equal-sized pieces and put in a saucepan. Cover with cold water and a lid, bring to the boil, then simmer on a medium heat for 10 mins, or until the potatoes and parsnips are soft (not falling apart).

3. Meanwhile, gently put the eggs in a small pan of water and bring to the boil. Cook for 7 mins, then transfer to a bowl of cold water and leave to cool. Once cool, peel and chop them.

4. When the fish is cooked (it should be firm to the touch and flake easily), remove from the milk, along with the onion, using a slotted spoon. Strain the milk into a jug and keep it for the mash.

5. Flake the fish into bite-sized chunks (checking for bones) and place in the bottom of a casserole dish, then add the onion, sweetcorn and peas.

6. Add the herbs, lemon zest, prawns (if using), hard-boiled eggs and the crème fraîche. Season and mix well.

7. Drain the parsnips and potatoes in a colander, and return to the saucepan. Add the nutmeg, white pepper, mustard and a knob of butter and mash well.

8. Taste to check the seasoning. Cover the fish filling with the mashed potato and, using a fork, create a wavy pattern, if you like. Sprinkle over the grated cheese.

9. Place in the oven for 20 mins or until the cheese is melted and golden brown, remove from the oven using oven gloves and serve with steamed crunchy carrots and broccoli.