Mince ginger, lemongrass, chillies and garlic with a touch of salt in a processor to make a paste. Stir fry the paste in half the oil in a wok over a very high heat for about a minute or so.
Briefly pulse the chicken breasts until coarse minced but not mushy. Tip the remaining oil into the wok with the chicken, toss through and stir fry until brown, then stir in the sugar and fish sauce, and fry until things look sticky and a little caramelised.
Take off the heat and toss through all the remaining ingredients and serve with crunchy leaves, and extra lemon or lime wedges to squeeze over.
Tip: To make toasted rice, toast 2 tbsp uncooked rice in a heavy pot until golden brown all over. Keep shaking the pan so that it doesn't burn. Cool and whizz to a fine powder in a coffee grinder or spice mill.