Method

1. For the hake, sprinkle one side of the hake with salt flakes. Set aside.

2. For the mushroom purée, heat the butter in a saucepan over a medium heat. Add the onion and garlic and season with a pinch of salt. Fry for 3-4 minutes, or until softened.

3. Add 200g/7oz of the button mushrooms and continue to cook for a further 1-2 minutes, stirring regularly. Pour in the sherry and bring to the boil, then add the dried mushrooms. Reduce the heat until the mixture is simmering and continue to simmer until most of the liquid has evaporated.

4. Add the double cream and return the mixture to the boil. Reduce the heat until the mixture is simmering, then simmer for 4-5 minutes, or until the volume of liquid has reduced by one-third. Remove from the heat and set aside to cool slightly.

5. In a food processor, blend the mushroom mixture to a purée, adding the yoghurt as you blend. Strain the purée through a fine sieve into a clean saucepan, then keep warm over a low heat.

6. For the celery root, bring 200ml/7fl oz water to the boil in a frying pan. Add the butter and a pinch of salt, then add the celery root and reduce the heat until the water is simmering. Continue to simmer for 20-25 minutes, or until most of the water has evaporated. Baste the celery root with the buttery juices remaining in the pan, then sprinkle over the thyme leaves and set aside. Keep warm.

7. For the mushroom purée, sprinkle the remaining mushrooms with sea salt and set aside for 5 minutes.

8. For the hake and butter sauce, sprinkle the flour onto a plate. Dust the hake in flour to completely cover.

9. Heat the oil in a frying pan over a medium heat. Add the fish and fry for 5-6 minutes, or until crisp and golden-brown on one side. Turn the fish over, add the butter and cook for 4-5 minutes, or until the hake is crisp and golden-brown on both sides and the butter has turned brown.

10. Add the malt vinegar and thyme to the pan, then baste the fish in the butter and vinegar mixture. Remove the fish from the pan.

11. Add the sugar to the pan, stirring it in the butter and vinegar mixture until dissolved. Stir in the chopped celery leaves.

12. To serve, put a spoonful of the mushroom purée into the centre of each plate. Place one piece of celery root on top with the hake alongside. Garnish with the salted mushrooms and a few sliced celery leaves, then drizzle the butter sauce around the edge of the plates. Finish with the toasted hazelnuts.