Boil the chicken: Place the whole chicken in a large pot, cover with water and bring to a boil. Lower to a simmer and cook until fully cooked through, about 40–45 minutes depending on size.
Cool and shred: Remove the chicken and let it cool (or plunge it into an ice bath to keep the skin firm). Shred the meat into bite-size pieces. Save the broth for phở or soup.
Make the dressing: In a mortar and pestle, pound the Thai peppers, salt and black peppercorns into a coarse paste. Stir in the lime juice.
Prep the aromatics: Thinly slice the red onion and roughly chop the rau răm.
Toss: In a large bowl, combine the shredded chicken, red onion and rau răm. Pour over the dressing and toss well. Taste and adjust with more lime or salt.
Notes
Use the broth: Boil the chicken for phở gà or another soup and use the meat for this salad, just like we do.