Place the mince in a large bowl and combine with the whisked egg, chopped onion, herbs and season well with salt and pepper.
Divide the mixture in four and roll into balls. Flatten with the palm of your hand so the patties are about 3cm thick. Wet hands slightly to help stop mixture sticking
Set on a plate and refrigerate for 30 minutes.
Meanwhile, make the slaw by combining the cabbage, carrot and red onion in a large bowl.
Whisk together the yoghurt, olive oil, mustard and lemon juice in a small bowl. Season with sea salt and black pepper to taste.
Pour the dressing over the vegetables and toss well. Set aside while you cook the burgers.
Cook burgers under a medium hot grill for 15 minutes, turning halfway through cooking. Check the burgers are cooked through before serving.
Serve inside a wholemeal bap with healthy slaw and cheese. For a healthier option, just serve with a big dollop of slaw and no bap.