Heat a frying pan until hot, add the butter and turbot and cook on each side for 2-3 minutes until just cooked through.
Bring a large pan of salted water to the boil, add the langoustines and boil for 3-4 minutes until cooked and then drain. Set 4 whole ones aside as a garnish.
To enable the meat to be prized out when served part of the shell needs to be removed. Turn the langoustines over to reveal the belly and using a pair of scissors, cut along each side and remove the shell to expose the sweet and tender meat.
Method for the potatoes and leeks:
Place the potatoes into a pan of water, bring to the boil and simmer for 12 minutes until tender.
Drain and toss in a little butter, salt and black pepper.
Bring a separate pan of water to the boil, add the leeks and cook for 3-4 minutes until tender.
Drain, toss with a little butter, salt and black pepper.
Method for the sauce:
Place the cream and star anise into a saucepan and bring to the boil.
Simmer until reduced by half.
Gradually beat in the butter, a little at a time.
When all the butter is incorporated, remove from the heat.
Add the chives, dill and lemon zest and season with salt and black pepper to taste.
Place the turbot into the centre of the plate.
Scatter the langoustines around and the potatoes to one side, the leeks to the other.