Make the Nuoc Cham:

1. Combine the lime juice, fish sauce, sugar, water, garlic, and chile if using. Mix until the sugar has dissolved. Set aside or refrigerate until ready to use.

Marinate and cook chicken:

1. Combine lemongrass, garlic, lime juice, fish sauce, oyster sauce, light brown sugar, and oil. Stir together.
2. Put the chicken in a bowl or a plastic zipping bag and pour the marinade on top. Refrigerate overnight or for at least 4 hours.

To Prepare:

1. Heat the broiler on high and place the oven rack about 6 inches from the top.
2. Take the chicken and lay it on a baking tray. (You can line the tray with foil to help with cleanup). Place the chicken on the rack and cook for 7-8 mins.
3. As different broilers cook at varying strengths, keep an eye on your chicken and either lower the heat or move the chicken further away from the heating element if you see the chicken starting to char too quickly.
4. Flip the chicken and continue to cook for an additional 7-8 mins. Let cool slightly and then cut into bite sized strips 
5. Bring a pot of water to boil. Add the noodles and stir with tongs or chopsticks and cook for 1-2 minutes until chewy and soft. Then drain in a colander under running water to cool. Set aside to drain off all water.
6. Assemble the bowls: Divide the noodles and place into large bowls. Top with the chicken and add a little lettuce, beansprouts, carrots, cucumber, and red onion to the bowls. Garnish with the cilantro, mint, and a wedge of lime, and a sprinkle of red chiles. Serve with the sauce on the side for people to help themselves.