Pre-heat the oven to 200ºC.
Mix together the cornflour, salt and cayenne pepper and place on a plate.
Beat together the egg whites and milk with a fork and place on a plate.
Dip the onion rings in the cornflour mixture, turning to coat on all sides.
Dip the floured onion rings in the egg white mixture, turning to coat on all sides.
Place the breadcrumbs on a plate and dip the onion rings in the breadcrumbs, turning to coat on all sides.
Spray 2 baking trays with low calorie cooking spray and use to grease the tray.
Place the bread-crumbed onion rings on the baking trays.
Mix together the yoghurt, garlic granules, salt, pepper, lemon juice and chives. Place the yoghurt dip in a small serving bowl.
Place the onion rings in the pre-heated oven for 20-25 minutes, turning occasionally, until the onion is tender and the breadcrumbs are golden.
Serve the onion rings with the dip and garnish with chives.