200 g cold unsalted butter (diced and kept in the fridge)
1 tblsp chopped chervil
Peel the potatoes and boil them until soft. Dry out to remove any excess moisture and add the butter and cream. Mash with a potato ricer to give a smoother texture. Season with salt and pepper and then add the herbs. Cover and leave aside.
For the Beurre Blanc heat the oil in a saucepan then add the shallots over a low heat until soft but not brown. Add the bay leaf, lemon juice, zest and white wine. Increase the heat and reduce by half. Add the cream and reduce by half again. Remove the pan from the heat and using a balloon whisk, add the butter one cube at a time. When all the butter has been incorporated add the chervil. The sauce will keep for up to 1 hour
Take the core out of the fennel bulbs and slice the fennel very thinly using a Japanese mandolin or a very sharp knife. Cook he ribbons in boiling salted water until tender. When cooked remove from the water and drop in the chives and season. Drizzle a little olive oil over to keep them from oxidizing.
Score the skin of sea bass with a very sharp knife to stop the skin from shrivelling. Season with salt and pepper and drizzle with olive oil. Place skin side down on a hot pan and cook for 2 minutes depending on the thickness. Carefully turn over the fillets and cook for another 2 minutes. Add a squeeze of lemon juice just before the end of the 2 minutes.
To serve spoon a portion of herb potato in the centre of the plate. Place some fennel ribbons on top of the herd potato and then place the fillet on top. Spoon the chervil beurre blanc around the plate and serve. The plate can be garnished with some wilted spinach to improve the look of the plate.