In a small bowl, combine all the ingredients. Set aside.
Cut the stalks of lemongrass into small pieces and finely chop in a food processor.
Add the peanut oil, sesame oil, broth and half the nuoc cham sauce. Mix thoroughly.
Pour the marinade into a glass dish or sealable plastic bag. Add the chicken. Cover the dish with plastic wrap or seal the bag and refrigerate for 2 hours or overnight. When in a hurry, marinate for 30 minutes at room temperature.
Preheat the grill, setting the burners to medium-high. Oil the grate.
Grill the chicken for 3 to 4 minutes on each side or until cooked through. On a work surface, slice the chicken and set aside.
Divide the noodles, lettuce and cucumber into bowls. Add the chicken and sprinkle with the peanuts. Drizzle with the remaining nuoc-cham sauce.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.