Heat a large saucepan over a medium-high heat and add the oil. Add the chicken and fry for 5 mins or until well-browned on all sides. Tip in the vegetables and cook for a further 5 mins until starting to soften. Add the garlic and pearl barley, then pour over 500ml water. Cover and leave to simmer for 25-30 mins, stirring occasionally.
Meanwhile, put all the dressing ingredients in the small bowl of a food processor and blitz until very finely chopped. Transfer to a bowl and set aside until serving.
When the pearl barley is soft, but still with a little bite, and most of the liquid has been absorbed, it’s ready to serve. Season to taste and divide the risotto between two plates, adding spoonfuls of the dressing, to serve.