Trim any fat from the thighs and cut the flesh into bite-sized pieces.

Remove the coarse outer layers from the lemon grass and trim the top and base.

Chop the rest – the softer bit of the lemon grass – as finely as you can.

Put half of this into a bowl with the fish sauce, caster sugar, half the chillies, all the garlic and the chopped chicken.

Mix together with your hands, cover with cling film and put into the fridge.

Leave to marinate for at least four hours; overnight is even better.

Bring it to room temperature before cooking.

Heat the oil in a wide-based saucepan or a wok set over a medium heat.

Add the chicken and cook on all sides, getting a really good colour all over it.

Add the reserved chillies, reserved lemon grass and the onion and stir-fry until the onion starts to soften.

Be careful not to burn the chillies or the lemon grass.

Pour in the stock, then reduce the heat, cover and allow the chicken to cook for about five minutes.

Remove the lid, increase the heat and continue to cook until the liquid is reduced.

You want a mixture that is wetter than a stir-fry but drier than a braise.

Add lime juice to taste, then check for seasoning and sweet-sour balance, adjusting with sugar and lime.

Sprinkle with the amaranth leaves or coriander and sesame seeds, if you like, and serve with brown rice and stir-fried greens.