To make the dressing, blanch the parsley in boiling water, then immediately refresh in iced water

Add the blanched parsley and oil to a high-power blender, blitz for 3 minutes then transfer to a double-layered muslin cloth (or coffee filter) suspended over a jug. Leave to strain until all the clear oil has passed through

Finely chop the lemon zest and garlic until very smooth. Chop the rest of the parsley and set aside

Mix the lemon zest, garlic and lemon juice with the herb oil and set aside in the fridge until ready to serve

To prepare the leeks, blanch in salted boiling water for a few minutes. Refresh in iced water, drain and set aside

To make the mash, boil the potatoes then allow to steam and dry. Pass through a drum sieve then beat in the butter and milk until silky smooth. Season to taste and keep warm

Preheat the oven to 200°C/gas mark 6

Brush the turbot portions with oil, season with salt and bake in the oven for around 5 minutes. Drizzle the blanched leeks with a little oil and bake in the oven with the fish

Check if the turbot is ready by pushing the back of a spoon along the bone of the fish, if you feel resistance it needs a little longer in the oven

Leave the fish to rest for around 3 minutes, then peel away and discard the skins

To serve, add a spoonful of mashed potato to each plate and place the leeks to one side. Place the turbot on top of the mashed potato and drizzle the dressing around the plate. Garnish with chopped curly parsley and serve