Step 1

Mix lime juice, soy sauce, palm sugar, chile powder, and 1 tsp. salt in a large bowl to combine; set dressing aside.

Step 2

Toast rice in a dry medium skillet over medium heat, stirring occasionally, until golden and nutty-smelling, 6–8 minutes. Transfer to a spice mill and let cool, then coarsely grind. Set rice powder aside. Wipe out pan.

Step 3

Heat oil in same pan over medium. Cook shallots and lemongrass, stirring often, until softened, about 4 minutes. Scrape into bowl with reserved dressing.

Step 4

Add tofu, 2 Tbsp. sesame seeds, and reserved rice powder to bowl and gently toss to combine. Season with salt and add more chile powder and lime juice if needed.

Step 5

Stir herbs into larb and serve with lettuce leaves and more sesame seeds for assembling.