Take three large carrots, wash and scrape and cut them into slices, put
them in a saucepan with half an onion, a stick of celery, and a bay
leaf, more than cover with boiling water and cook until tender. Remove
from the fire, take out the bay leaf and rub the vegetables through a
sieve with the water they were boiled in. Put back in the saucepan. Rub
a generous tablespoonful of butter with half a tablespoonful of flour,
and stir into the puree, add to it a cup and a half of boiling milk,
stir until thick, add pepper and salt to taste. Take from the fire, and
stir into it one egg yolk beaten with two tablespoonfuls of cream. Serve
at once.