Both Som Tum and Yam Neua are usually set atop a small bed of undressed shredded lettuce, which acts more like a garnish than a base. I chose to use mizuna, which is normally found in Japanese cooking, to give the beef an extra peppery bite.
For the Salad:
3/4 lb flank steak
¼ cup fresh mint leaves, coarsely chopped
¼ cup cilantro leaves, coarsely chopped
1 shallot, sliced very thin
½ pint cherry tomatoes
1/4 cup chopped unsalted roasted peanuts
3-5oz mizuna (or baby arugula)
For the Dressing:
2 cloves garlic, pushed through a press
2-3 tsp siracha (or you can use minced Thai chilies)
½ tsp chili powder
2 tbsp sugar
5 tbsp fish sauce
3 limes, juiced
½ tbsp sesame oil
Trim off any excess fat from the steak and season it well with salt and pepper on both sides. Brush a ridged indoor grill pan with oil and set it over a high flame. When the pan is hot, set the steak down diagonally on the pan and cook until dark marks have formed. On the same side, shift the steak so it lies on the opposite diagonal of the pan. This will create a beautiful cross-hatch. Repeat on the other side, and cook until medium rare (when the meat has firmed up, but still has some give when prodded). Cover the steak with tin foil and set aside to rest for at least 15 minutes. In the meantime, combine the fresh herbs, shallot, tomatoes, and half of the peanuts in a medium mixing bowl.
In a small bowl, combine all ingredients for the dressing. One the meat has properly rested, transfer it to a cutting board and slice it into thin strips on a diagonal (your knife should be positioned at a 45 degree angle). Toss the meat together with the salad mixture and the dressing. To serve, create a large bed of mizuna on two plates, and top each with a large helping of beef salad (making sure to keep some of the liquid). Garnish with the remaining peanuts and a few leaves of cilantro.