|Place pork chunks on large plate in single layer. Freeze meat until it starts to harden around edges but is still pliable, about 15 to 20 minutes.|
|Place half of the meat in the food processor and pulse until coarsely chopped, using 5 to 6 1-second pulses. Transfer ground meat to a medium bowl and repeat with the remaining pieces. Stir 1 tablespoon fish sauce into ground meat and marinate for 15 minutes in the fridge.|
|Heat the rice in small skillet over medium-high heat and cook, stirring constantly, until deep golden brown, about 5 minutes. Transfer the rice to a small bowl and cool for about 5 minutes. Grind the rice with spice grinder, mini food processor, or mortar and pestle until it resembles fine meal, 10 to 30 seconds (you should have about 1 tablespoon of rice powder).|
|Simmer the broth in a 12-inch non-stick skillet over medium-high heat. Add the pork and cook, stirring frequently, until about half of the pork is no longer pink, about 2 minutes. Sprinkle 1 teaspoon of the rice powder over the pork; continue to cook, stirring constantly, until the remaining pork is no longer pink, 1 to 1.5 minutes longer. Transfer the pork to a large bowl and cool for about 10 minutes.|
|Add the remaining 1.5 tablespoons of fish sauce, remaining 2 teaspoons of rice powder, shallots, lime juice, sugar, red pepper flakes, mint, cilantro, and kaffir lime leaf (if using) to the pork; toss to combine. Serve with lettuce leaves and hot sauce on the side.|
source: Cook's Illustrated
Kaffir lime leaves can be stored in the freezer.