In a small bowl, combine all the ingredients. Set aside.
In a food processor, finely chop the lemongrass. Add the peanut oil, sesame oil, chicken broth and ½ cup of the nuoc cham sauce. Mix thoroughly.
Pour the lemongrass mixture into an airtight container or sealable bag. Add the chicken and seal the container or bag. Refrigerate for 2 hours or overnight. If desired, you can freeze the chicken at this stage.
Preheat the grill, setting the burners to medium high. Oil the grate.
Drain the chicken and discard the marinade. Grill the chicken for 3 to 4 minutes on each side, or until cooked through. Slice the chicken and set aside.
In a pot of boiling water, submerge the vermicelli. Remove the pot from the heat and let sit for 3 minutes or until the noodles are tender. Drain.
To serve, on six plates, layer the vermicelli, lettuce and cucumber. Top with the sliced chicken. Sprinkle with the peanuts and green onions. Drizzle with the remaining nuoc cham sauce and serve with lime wedges.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.