Place each chicken breast between 2 sheets of greaseproof paper and pound it gently until the fillet is about 15mm thick.

To make the marinade,place all the ingredients in a food processor and process until they are well combined but not completely puréed.

Marinate the chicken breasts for 1 hour.

Meanwhile,make the relish.

Use a sharp knife or Japanese mandolin to finely slice the cucumber and celery.

In a bowl,whisk the oil,vinegar and mustard together,then season with salt and pepper to taste.

Fold in the yoghurt. Add the cucumber,celery,tomato and mint leaves,and mix to combine.

Heat a barbecue or grill pan to hot.

Remove the chicken from the marinade and grill it,skin side down,for 2 minutes,then turn and cook for a further minute or until just cooked through.

Rest in a warm place for about 1 minute.

Place the chicken pieces on a platter,and serve with the relish on the side.