Begin the day before by making the tarragon oil. Add the tarragon and oil to a high-powered blender and blitz until smooth and vivid green

Transfer the oil to a sieve lined with a double layer of muslin or a coffee filter. Set over a container to collect the oil that drips through and leave in the fridge overnight – the oil should be bright green and crystal clear

Slice the leeks into rounds and blanch in salted boiling water for a few minutes. Refresh in iced water, then drain well and smoke in a cold-smoker for 2 hours

To make the oyster sauce, add the cucumber, shallots, horseradish cream, vinegar and sugar to a blender. Blitz until smooth for 3 minutes

Tip the liquid into a fine chinois and allow to strain through to remove the pulp. Set the strained liquid aside

Add the egg yolks, lemon juice and oysters to a blender and blitz until smooth. With the motor running, slowly add the oil in a thin stream to emulsify

Scrape down the sides of the blender. Turn on the blender again and slowly add the cucumber stock until you reach the desired consistency and flavour

Preheat the oven to 180°C/gas mark 4

Blanch the spring onions in salted boiling water then refresh in iced water. Drain and set aside

Place the smoked leek pieces in a baking tray and heat through in the oven

Preheat a deep-fryer to 190°C

To make the crispy oysters, dip each oyster first in the flour, then the egg, and finally the breadcrumbs. Fry in the hot oil for 2 minutes until crisp and golden, then drain on kitchen paper and season with salt

Heat a chargrill pan, brush the blanched spring onions with oil and cook until lightly charred

To cook the lemon sole, brush each fillet with a little oil, season with salt and grill under a hot grill for around 2 minutes, until just cooked through

To serve, sit the slices of smoked leek in the centre of each plate. Pour the sauce around the leeks and drizzle over the tarragon oil. Place a lemon sole fillet on top of the leeks, arrange the spring onion on the plate and top with a crispy oyster. Serve immediately