Make the rice powder. Add 2 tbsp of raw white rice to a dry pan over medium heat. Stir continuously for 5–7 minutes until deep golden and nutty-smelling. Remove from heat, cool briefly, then grind using a mortar and pestle, or pulse in a blender in small bursts until powdered.
Make the dressing. Combine fish sauce, lime juice, and sugar in a bowl. Whisk until the sugar dissolves. Add garlic, chilli, and half the rice powder. Taste it — you want salty, sour, sweet, and hot all at once. Adjust until nothing dominates.
Shred the chicken. Remove the skin and pull the meat from the bones. If cold, warm first — 60 seconds in the microwave will do. It must be warm when dressed to absorb the dressing.
Build the salad. Add the warm chicken to a large bowl with the bean sprouts, cucumber, coriander, and mint. Pour over the dressing and toss gently. Taste and adjust with extra lime or fish sauce if needed.
Plate and finish. Pile into bowls. Top with extra herbs, sliced chilli, the remaining rice powder, and a lime wedge. Eat immediately.
