Ingredients:

  Amount  Measure       Ingredient -- Preparation Method
--------  ------------  --------------------------------
   3                    serrano chilies
     1/4  cup           white vinegar
   1 1/2  pounds        flank steak
     1/4  pound         red onion -- sliced
   4                    green onions
     1/4  cup           lime juice -- plus:
   1      tablespoon    lime juice
   2      tablespoons   fish sauce (nam pla)
   1      teaspoon      ground roasted chilies *
   2      tablespoons   ground toasted rice **
                        red lettuce leaves
                        coriander sprigs
                        mint or basil leaves

Preparation:

1. Remove the stems, but not the seeds, from the chilies. Slice the chiles crosswise into pieces 1/8" thick. Place the sliced chiles and vinegar in a small serving bowl. Let it stand for at least 15 minutes. 2. Grill the beef to the desired doneness, preferably over charcoal. Slice it across the grain into strips 1/8" thick and 1 to 2 inches long. Put these in a large ceramic bowl. 3. Peel the red onion, remove the root portion, and slice the onion vertically into thin strips. Slice the green onion diagonally into thin pieces. Add both types of onion to the beef. 4. Add the lime juice, fish sauce, ground chilies, and ground rice. Mix well 5. Arrange a single layer of lettuce leaves on a serving platter, and place the beef mixture on top. 6. Garnish with sprigs of coriander and mint or basil leaves. 7. Serve at room temperature, the vinegar sauce (from Step 1) and rice. * Use small hot chilies about 3 to 4 inches long. Roast whole chile stems and all, in a dry wok or skillet until the color changes to dark red or brown depending on the chilies used. Be careful not to let them burn. When the chilies have cooled, remove the stems and seeds. Place the chilies in a food processor or blender and grind using short pulses. Pre-ground chilies are also commercially available, but often lack the "bite" of home ground ones and may be more expensive. ** Place uncooked rice in a dry wok or skillet and heat over moderate heat until deep golden brown, stirring frequently to keep from burning and to allow it to develop a uniform color. Watch the rice carefully after it begins to change color and stir constantly because it can burn easily at this stage. When it is a uniform deep golden color, remove from heat and allow to cool to room temperature. Grind it to a fine powder in a blender or a spice grinder. This can be made in advance and kept in quantity so that there is always a supply on hand, but it is also easy to make up while preparing the dish. Source: "Thai Home-Cooking from Kamolmal's Kitchen" by William Crawford and Kamolmal Pootaraksa