Dry-toast 2 tablespoons of uncooked rice in a wok over high heat for about 5 minutes, stirring until dark golden. Grind to a fine powder.
Mix the rice powder with 3 tablespoons of water, 2½ tablespoons of lime juice, 2 tablespoons of fish sauce, and 2 teaspoons of brown sugar.
Heat 2 tablespoons of peanut oil in the wok over medium-high heat. Add 1 tablespoon of grated ginger, 2 minced garlic cloves, 1 lemongrass stalk, tender white part finely chopped, and 2 Thai chilies, seeded and chopped. Stir for 1 minute.
Add 500g of ground chicken and increase the heat. Cook for 3-4 minutes, breaking up clumps.
Add the sauce and cook for about 1 minute, until thickened and the chicken is cooked through.
Remove from the heat. Stir in ½ thinly sliced red onion, ⅓ cup of cilantro leaves, and ⅓ cup of mint leaves.
Spoon into 8 romaine lettuce leaves and scatter with 3 tablespoons of crushed peanuts.
