Boil water and blanch watercress for 15 seconds before refreshing in cold water.
Squeeze water from the watercress using a muslin cloth.
Blend watercress with 150ml rapeseed oil and salt until dark green.
Strain the oil through a muslin-lined sieve for one hour or overnight.
Heat 300ml rapeseed oil and 300ml sunflower oil in a pan to 50°C.
Poach fish for 8-10 minutes then drain on a wire rack.
Rest fish in a warm place for 5-10 minutes and char the skin with a blowtorch.
Fry the shallot in oil without browning.
Add 25ml cider, whitebait, and garlic then reduce liquid by half.
Simmer with double cream for five minutes.
Pulse the sauce in a blender and pass through a fine sieve.
Steam broccoli for 4-5 minutes until tender.
Trim kale into large pieces.
Heat vegetable oil in a deep-fat fryer to 160°C.
Fry kale until crisp while covering the fryer with a lid.
Drain kale on kitchen paper and season with sea salt.
Keep kale warm in a low-temperature oven.
Stir remaining 25ml cider into the sauce and season to taste.
Plate the sauce, drizzle with watercress oil, and top with fish and greens.