Step 1Crack the coconut and cut away pieces of the meat, then use a vegetable peeler to make thin (1-inch) strips until you have about one-third cup of thin strips. Toast the coconut strips on a baking sheet in a 350-degree oven for 15 to 17 minutes until golden. Remove, cool and set aside.
Step 2Combine the lime juice, fish sauce and sugar and let stand while preparing the salad. Taste and add more sugar, if desired.
Step 3Cut off the root end of the lemon grass stalks and discard. Use 6 inches of the lower part for the salad. Discard the rest, or save for another use. Remove the coarse outer layers of each stalk. With a very sharp knife, slice the lemon grass stalks crosswise as fine as possible. There should be about 1 1/2 cups sliced lemon grass.
Step 4Peel the shallots; quarter them lengthwise, then slice thinly. Trim the root end of the green onions and cut off part of the green end, leaving 1 inch of the green part. Cut the onions in half lengthwise, then slice thinly.
Step 5Heat the oil in a small skillet. Fry the cashews until golden, about 50 seconds. Drain on paper towels. Fry the dried shrimp until crisp, about 1 1/2 minutes. Drain on paper towels.
Step 6In a bowl, combine the cashews, shrimp, lemon grass, shallots and green onions. Just before serving, add the small pieces of Thai chile to the lime juice-fish sauce dressing, pour over the salad and toss well.
Step 7Place a large romaine leaf on a serving plate. Spoon the salad onto the leaf. Sprinkle on the coconut strips. Prepare a plate of tender romaine leaves (or the top halves of romaine leaves, center ribs removed).
Step 8To eat, use your hands to shape a piece of lettuce into a little cup, spoon salad into the lettuce, wrap and eat.