Preheat the oven to 200C/gas mark 6. In a small roasting tin, set the chicken breasts side by side and pour a little olive oil over them. Season with salt and ground black pepper and roast for about 20-25 minutes till the skin is pale gold and the juices run clear when the chicken is pierced with a metal skewer. Remove from the oven and set aside.
Make the dressing: put the lime juice and fish sauce in a small bowl or jam jar and stir in the sugar. Finely chop the chillies, then trim and finely slice the spring onions, discarding any dark, tough stems, and add both to the dressing.
Keep the mint and basil leaves whole and put them in a large mixing bowl. Wash, shake dry and then add the watercress or pea shoots to the herbs. Halve the pepper, discard the core and seeds, then finely slice the flesh into long, thin strips and add to the herbs. Halve, stone and thickly slice the peaches then add them to the bowl, too.
Remove the warm chicken from its bones, tear into thick pieces and add to the salad. Place the roasting tin over a moderate heat, pour the dressing into the tin and stir to dissolve any delicious chicken juices into the dressing. Pour the warm dressing over the salad and gently toss everything together.
