Try to obtain snails about 1/2" diameter. Starve them for 3 or 4 days to get rid of any toxic herbs they may have ingested. Wash snails in running water till all the slime is gone. Place them in a large pan and cover with water (2" or 3" above snails).
Add all the other ingredients. Cover the pan tightly. Heat the water over a very slow fire so that snails have time to extend heads outside shells.
Let boil slowly for the first hour. Skim and simmer for another hour,
Skim again and serve warm in saucers, with a little of the cooking liquid.
Use toothpicks or pins to extract snails from shell. Dip small pieces of bread in the cooking liquid. Refrigerates well - use any leftovers within a week. Suggested wines: Portuguese Vinho Verde, or a dry white wine.