Wash the lettuce, taragons, and chervil well, and shred them finely.
Peel the cucumber, and shred it also finely.
Melt the butter, and gently sauté the vegetables in it for five minutes, taking care they do not discolour.
Boil the stock in another saucepan, and, when boiling, pour it on to the vegetables.
Simmer gently until the vegetables are quite tender.
Beat the yolks of the eggs with the cream, and when the stock has cooled a little strain them through a hair sieve into it.
Put the stewpan by the fire, and stir until the eggs thicken, taking care that the stock does not boil, as that would curdle them.
Add pepper and salt to taste, and the soup is ready.
The crust of the French roll should be served in the soup; it should be baked in the oven and then cut into fancy shapes.