Soak the tongue in cold water for several hours.
Rinse the tongue under cold running water and rub lightly with salt.
Place, in a pan with water to cover and add the vegetables, herbs and spices.
Bring to a boil and cook over low heat for about 3 hours or until tender.
Remove the tongue from the pan and remove the skin.
Strain the cooking liquid and reserve 2 cups for the sauce.
Keep the tongue warm in the remaining cooking liquid.
Melt half of the butter, stir in the flour, and add the cooking liquid, stirring constantly until a smooth sauce is formed.
Combine the eggs with a little of the warm sauce and add this mixture to the sauce, stirring constantly.
Then, over very low heat, add the remaining butter and vinegar stirring constantly.
Do not allow the sauce to boil after the eggs are added.