Heat a medium frying pan until hot, then add the olive oil. Place the halibut fillets skin side down in the pan, cook for 3-5 minutes then turn the fillets over. Add 25g/1oz of the butter then remove the pan from the heat and set aside to rest.
Heat a medium frying pan until hot, add another 25g/1oz of the butter and the sprout tops and cook for 3-4 minutes until the sprout tops have wilted.
Meanwhile, place a large saucepan on the heat and add the white wine. When it’s boiling add the cockles, mussels and clams and place a lid on top. Cook for 2-3 minutes on a high heat.
When the shells have opened drain the shellfish, reserving the liquor, then remove the flesh from the shells. Discard any clams or mussels that have not opened.
Heat a medium frying pan and add half the remaining butter (50g/2oz). Fry the shallot until soft, add the shellfish liquor then cook until the volume of the liquid is reduced by half. Stir in the remaining butter in small pieces until the sauce thickens.
Add the picked cockles, mussels and clams to the pan and finish off with the chopped chives and chervil.
To serve, place the sprout tops in the centre of on the plate, add the halibut fillet and drizzle the sauce around the plate.