
Make the chicken marinade by combining the chicken, minced lemongrass, garlic, lime juice, fish sauce, soy sauce, brown sugar, and 1 tbsp of the vegetable oil in a bowl. Toss well, cover, and refrigerate for at least 1 hour or up to 24 hours.
In a small bowl, stir together the rice vinegar, white sugar, water, and chopped bird's eye chili until the sugar dissolves. Let the sauce stand for at least 20 minutes so the flavors meld.
Prepare the vegetables and herbs while the chicken marinates. Julienne the carrots and cucumbers, shred the lettuce if needed, and keep the bean sprouts, mint, cilantro, sliced red chili, and lime wedges ready for serving.
Soak the vermicelli noodles in hot water according to the package directions, about 3 minutes, until tender. Drain and rinse under cold water to cool them and prevent sticking.
Heat the remaining 1/2 tbsp vegetable oil in a skillet over medium heat, or preheat a grill. Remove the chicken from the marinade and shake off any large pieces of lemongrass so they do not burn.
Cook the chicken for 3 to 4 minutes per side, or until deeply golden and cooked through. Transfer to a plate and let it rest for 5 minutes.
Slice the rested chicken thinly. Divide the noodles among serving bowls, then arrange the lettuce, bean sprouts, carrots, cucumbers, mint, and cilantro on top.
Finish each bowl with sliced chicken, a generous spoonful of the sauce, sliced red chili, and lime wedges. Serve immediately, or place everything on platters and let everyone assemble their own bowls.




