From:
The Thorough Good Cook
Sauces: 3. A la Parisienne
This
sauce is composed of
Béchamel sauce, into which are put
mushrooms, blanched, and cooked
truffles cut up in very small pieces; also the tails of
shrimps peeled. Heat this, without boiling it, in a
metal-
bath, and see at the moment of serving that it is well
seasoned.