Directions

1Preheat the oven to 175°C (fan assisted).

2Place the white potato in a pan of cold salted water. Bring to the boil and then add the sweet potato. Simmer for 10-15 minutes or until the potatoes are soft, but not broken up. Remove from the heat, drain and return to the pan so they can dry out for a few minutes before ashing.

3Stir in the double cream and lightly season.

4In a large saucepan, bring the wine to the boil and add the stock. Add the onion, leek and bay leaf and simmer for few minutes to allow the onion and leek to braise. Add the fish and prawns and simmer for a further 2-3 minutes or until the fish is just cooked.

5Strain the poaching liquor into a measuring jug and place the fish and vegetables back in the pan.

To make the sauce:

1In a separate saucepan melt the butter. Add the flour to the butter, mixing continuously until it becomes a smooth paste and begins to bubble.

2Remove from the heat and gradually whisk in the poaching liquor until it is all incorporated.

3Return to the heat and bring to the boil, stirring continuously until the sauce is thick and smooth. Pour in the double cream, stir in the Dijon mustard, chopped parsley and season to taste.

To assemble and to cook the dish

1Gently mix the sauce with the fish and then transfer to an ovenproof dish allowing enough room to top with the mashed potato.

2Spoon or pipe the mashed potato over the pie, ensuring it is fully covered to prevent the filling from leaking.

3Place into a preheated oven for 20-25 minutes until piping hot and the mashed potato has started to colour.