How to Make It
Trim the root ends of the lemongrass and remove a total of 8 long outer leaves from the stalks. Tear the leaves into three 3-inch-long strands. Trim off and discard all but the bottom 3 inches of the stalks and finely chop 1 of the tender bulbs. Thinly slice the remaining bulb on the diagonal. In a mini processor, puree the chopped lemongrass to a fine paste.
In a bowl, combine the ground pork with the snails, ginger, minced chile, sesame oil, salt, pepper and lemongrass paste.
Gently bend a lemongrass strand in half and stick it inside a snail shell, bent side in, and with the 2 ends protruding. Stuff the shell with 2 teaspoons of the pork-and-snail filling, working it between the lemongrass ends. Wipe the rim of the shell. Repeat with the remaining lemongrass strands, shells and filling.
Line a steamer rack with lettuce leaves and set the stuffed shells on top. Steam the snails until hot to the touch and cooked through, about 8 minutes.
Meanwhile, heat the oil in a small saucepan. Add the sliced lemongrass, julienned chile and scallion and cook over moderate heat until fragrant, about 1 minute. Pour the soy sauce into a heatproof serving bowl. Stir in the scallion-and-chile oil and serve with the snails.