Heat oil in a pan over medium heat. Add the minced chicken and cook until no longer pink, about 5-6 minutes, breaking up any clumps with a wooden spoon.
Transfer the warm chicken to a mixing bowl and immediately add the fish sauce and lime juice. Toss thoroughly and let rest for 10 minutes to marinate and cool slightly.
Sprinkle the toasted rice powder and chili flakes over the chicken mixture and mix well.
Add the chopped mint, cilantro, green onions, and sliced shallots. Gently fold everything together until well combined.
Taste and adjust seasoning if needed, adding a pinch of sugar to balance flavors if desired.
Arrange fresh lettuce leaves on a serving plate and spoon the larb mixture over them. Alternatively, serve the lettuce leaves on the side for wrapping.
Garnish with cucumber ribbons if using and serve immediately with lime wedges on the side for an extra squeeze of freshness.
