Peel cucumbers and cut into 1cm slices. Simmer in a pan with the shallot and stock for 15 to 20 minutes until soft.
Rub through a nylon strainer or work in a blender until smooth.
Melt the butter, add the flour or cornflour off the heat and cook until straw-coloured and marbled in appearance.
Blend in the cucumber liquid, stir until boiling, then season with salt and pepper and simmer for 2 to 3 minutes. (I freeze the soup at this stage.)
Liaison - Work the yolks and 8 tablespoons cream together in a bowl with a wooden spoon, draw the heated soup off the heat and then very slowly add about 3-4 tablespoons of the hot soup to this liaison.
Return this to the saucepan a little at a time, then reheat gently, without boiling, until the soup has thickened.
Colour the soup delicately, adjust the seasoning and pour into a container ready for chilling. Cover the soup to prevent a skin forming and when cold place it in the fridge or in a bowl packed with ice to chill.
Garnish with the mint or chives and whipped cream.
Remember to chill the tureen and soup cups before serving.
Put a rounded tablespoon of lightly whipped cream in each cup or the equivalent in a tureen and stir it in gently to give the soup a streaky look, sprinkle with mint or chives.