Cut up the chicken thighs into bite-sized pieces
Mix together the marinade ingredients in a bowl, add the chicken pieces and coat well. Leave for a while in the fridge - for as long as is practical.
For the caramel, stir 1 Tbsp water with the sugar in a small heavy based saucepan over a low heat until it dissolves. Turn up the heat and leave to get sticky brown before taking off the heat and stirring in the other 2 Tbsp of water.
Heat up a wok (or big frying pan) well then add the oil. Let it get properly hot before adding the lemongrass and onion. Stir constantly until softened then add the chicken and caramel. Stir fry for about 5 minutes to make sure the chicken is cooked through.
Serve with fragrant Jasmine rice and topped with some coriander.