Cut the eel in pieces of about 2 inches in length, put them in an earthenware vessel, sprinkle freely with salt, and let them stand in a cold place for 3 or 4 hours. Now lay them in a saucepan, closely packed, moisten with the white wine, sprinkle with parsley, cover the saucepan and simmer till the pieces of eel are quite tender.
For the sauce, melt the butter in a saucepan, add the finely chopped yolk of egg, stir well and add the other ingredients. Serve in a sauceboat. Garnish with slices of lemon.