Add all the ingredients listed under salad dressing and whisk it well. Check the seasoning. You can make it 1 day ahead and keep it refrigirated.
Poach Chicken
In a saucepan add chicken stock, coconut milk, crushed lemongrass, salt, and pepper. Once the mixture comes to a boil, reduce the heat and let the liquid simmer.
Add chicken breast to the liquid and let it cook at a low temperature for 7-8 minutes. Switch off the flame and let it rest in the liquid for 10 minutes. Then remove the chicken from the liquid, keep it covered until it is cold enough to handle.
Shred and keep aside. You can make it 1-2 days ahead of time and store it in the refrigerator.
Prep Veggies and rice Vermicelli
To cook rice vermicelli, place dry noodles in a heatproof container and pour hot water until it is completely covered. Let it soak for 10-15 minutes. Drain and keep.
Cut all veggeis, herbs, and keep them ready.
Assembling Salad
In a large salad bowl, add veggies, drained cold rice noodles, shredded chicken, herbs, fried shallots, and roasted peanuts. Pour half of the prepared dressing. Toss salad and serve with more fried shallots and peanuts on the side.