Wash the lights thoroughly. Wash, trim and coarsely chop the bouquet garni. Cut the onion into wedges.

Bring the water to the boil in a saucepan with a generous pinch of salt, the peppercorns, bay leaves, vinegar, herbs and onion.

Add the lights and simmer gently for 1 hour, removing any scum from the surface of the water as it forms. Drain the lights, place them between two boards, put a weight on top and leave for 12 hours.

Strain 375 ml (13 fl oz) of the cooking water. Cut the lights into fairly thick strips.

Melt the butter in a saucepan, stir in the flour and cook until golden. Gradually add the cooking water. Boil for 10 minutes, stirring frequently, then season with the lemon juice, wine, pepper and salt.

Add the lights and simmer for 15 minutes. Stir in the soured cream.