Pick off the stems from half a peck of sorrel ; wash it in several waters, drain, and chop up with a head of well-cleansed lettuce. Add half a bunch of chervil, and chop all together very fine. Place all in a saucepan, stir well together on the hot stove for three minutes, and then place it in the oven until the vegetables are well dissolved ; then add an ounce and a half of butter, and stir again for about ten minutes, or until the sorrel is reduced to a pulp. Season with a pinch of salt and half a pinch of pepper, and pour into it a thickening of two egg yolks and half a cupful of cream ; stir well, without boiling, and serve.