Preheat the oven to 200°C/180°C fan/gas 6. In a small food processor, blitz the bread and walnuts to a fine crumb.
Put the chicken in an oven dish, season, then spread 1 tbsp mayo over each breast. Scatter over the crumb, pressing gently to stick. Bake for 25 mins or until cooked through and golden.
Meanwhile, combine the carrot, cabbage, beetroot and salad onion in a mixing bowl. Add the yoghurt and remaining mayo and toss to combine. Fold through the mixed seeds and the flat-leaf parsley, if using.
Serve the chicken with the slaw. Leftover slaw will keep in a chilled airtight container for up to 3 days.
