Put the snails in a basin of water until their heads come out of the shell (we do not use those that do not come out of their shells) and wash them well several times. Put the snails together with plenty of salt in boiling water. When the water starts to foam, change it with a clean one, add the vinegar and leave it for another 10 minutes. Remove the snails from the heat and rinse with cold water. Salt the snails and flour them well. Put the oil in a pan until it’s hot and add the snails with the opening down for 3-4 minutes. Add the rosemary, salt and pepper, stir and simmer with the wine. Let them boil and they are ready.