Press the foot which lies along the curve of the shell of the snail. If it retracts the snail is alive. Place it between several folds of newspaper and crack the shell with a hammer untill all of the snail is exposed. The scallop-like muscle attached to the disk is the edible portion. The greyish and ivory-colored portion tapers to a narrow strip. Cut of the muscle at the narrow strip, and free it from the soft texture next to it. discard the remainder of the snail. Cut of the foot, the edible tubule, the bony cartilage and the gelatinous material surrounding the cartilage. Slice off the disk and the greyish outer layer of the scallop. Discard all these portions, saving only the ivory-colored scallop.
Slice it very thin, gripping the muscle with a cloth to prevent it from slipping about. Three snails yield enough thin slices to measure 12 fluid oz.
Make the sauce. Mix all the ingredients together in a small saucepan and heat gently: 1 tablespoon oyster sauce, 1 tablespoon light soy sauce, 2 tablespoons chicken stock, 3/4 level teaspoon sugar, 1/4 level teaspoon MSG [ve-tsin], 2 slices ginger finely slivered, 1 spring onion slivered, 3 tablespoons oil.
Have ready a large piece of cheesecloth placed over a bowl, a slotted spoon and a pair of chopsticks. Bring 5 pints of water to the boil with 1 piece of ginger and 1 spring onion. Remove the ginger and the spring onion. Add 2 tablespoons vinegar to the water, keep it at a rolling boil. Bring the sauce up to simmering point.
Throw the snail slices all at once in the acidified water. Almost immediately remove all the slices with the aid of the slotted spoon and chopsticks, and place them in the cheesecloth. Wring the water out of the slices, and drop the slices into the simmering sauce, which must now be brought to high heat. Sauté for 15 to 20 seconds, and serve immediately.