Preheat the barbecue or oven to 180C/350F/Gas 4.
For the spatchcock chicken, slash each chicken leg two or three times with a sharp knife. Season with salt and freshly ground pepper, sprinkle with chopped rosemary and thyme leaves and drizzle with extra virgin olive oil.
Transfer to a roasting tin. Place skin-side upwards and tuck the whole garlic cloves underneath. Roast on the barbeque or in a preheated oven for 50 minutes to an hour, or until the juices run clear
For the fennel and mango salad, lightly crush the hazelnuts in a pestle and mortar or place in a plastic bag and use a rolling pin to break them up. Set aside.
In a bowl, mix together the mango and fennel with the olive oil, lemon juice and mint. Season to taste with salt and pepper.
To serve, cut the chicken into portions, then divide the salad between plates, scatter over the toasted hazelnuts and crumble over the feta cheese.