Peel and grate the onion, then combine the beef mince, the onion, mixed herbs, egg and breadcrumbs in a large bowl. Season with salt and pepper then shape mixture into eight thick rissoles (about ¾" - 2cm thick). Place on a large plate.
Heat the duck fat (or oil) in a frying pan over medium-high heat. Add the rissoles and cook for 3 to 4 minutes each side or until cooked through. Serve rissoles with peas, carrot, potatoes and gravy.