Halve the fennel vertically, slice lengthways to a thickness of 4 – 5mm then blanch in a pan of boiling water with 1 teaspoon of salt, 1 teaspoon of sugar, and the lemon juice, for 10 – 15 minutes or until tender. Strain well.

Fry the sliced shallot in 20g of butter and 1 tablespoon of olive oil until translucent. Add ½ teaspoon of sugar, ½ teaspoon of salt and the fennel seeds and fry gently for 2 minutes.

Add the blanched fennel to the shallot pan and mix.

Transfer to a shallow, ovenproof dish large enough to hold all of the fillets in one layer. Set to one side.

Next, prepare the beurre blanc. Gently fry the chopped shallot in 20g butter until translucent, add the vermouth and the wine. Simmer to boil off the alcohol.

Add the fish stock, lemon juice and sugar, then boil until it has reduced by about a third.

Remove from the heat and strain into a small saucepan. Set to one side.

About one hour before serving, heat your oven to 180°C / 350°F / gas mark 4.

Add 100ml of wine to the fennel, dot the top with small pieces of butter, then place in the oven for an hour. Make sure it doesn’t brown too much.

Take the dish out of the oven and lay the fish fillets on top of the fennel. Season the fish with salt and pepper and top each with a thin slice of butter.

Return to the oven for 10 – 12 minutes.

While the fish is cooking, heat up the beurre blanc base until it is beginning to boil.

Remove from the heat and gradually whisk in the cold butter two pieces at a time, until an emulsion forms that coats the back of a spoon. Season.

Check the fish; it should be just set when cooked.

Using a spatula, carefully lift a fillet, and the fennel underneath it, and place on a plate. Spoon some beurre blanc over the fish and serve with new potatoes and perhaps a few fine green beans.