Poach the chicken breasts: place the chicken breasts in a pot large enough so they’re sitting on the bottom of the pot; pour in just enough water to cover the chicken pieces; add the dried ground coriander, ground ginger and dried lemongrass or a stalk of fresh lemongrass, and kaffir lime leaves; bring the water to a boil, then immediately reduce the heat to low and simmer for 5-10 minutes or until the chicken breasts are done. Use a thermometer to check that the internal temperature is 74°C/ 165°F.
Remove the chicken breasts to cool, then when they’re cool shred the chicken pieces by hand into strips.
Make the dressing: to a mixing jug with spout, pour in the Vietnamese fish sauce, lime juice, sugar, sliced chillies, and chopped garlic, and stir vigorously until well combined and the sugar has dissolved.
To a large mixing bowl, add the shredded cabbage, grated carrots, sliced purple shallots, and half of the fresh herbs, and use your hands to combine well, then add the salad dressing and use a spoon to thoroughly combine, then add the shredded chicken just before serving and combine.
When you’re ready to eat, pile the salad onto a serving dish, sprinkle on the rest of the fresh herbs, pan-roasted peanuts and crunchy fried shallots, and serve immediately.