Preheat the oven to 160°C conventional oven/ 140°C fan-forced (325° Fahrenheit/Gas 3). Line a large baking tray with baking paper.
Rub the olive oil, rosemary and thyme all over the lamb. Season lightly with salt and pepper. Use the point of a sharp knife to make 4 small incisions in the lamb approximately 2cm deep. Push a garlic clove into each incision. Transfer the lamb to the baking tray.
Scatter red onion over and around the lamb. Pour over the white wine, then add the hot chicken stock. Bake for 4 hours or until the meat falls off the bone easily.
Remove lamb from the oven and allow to cool for 10 minutes before slicing. Place the sliced lamb on a serving dish and spoon the pan juices and onions over the top – buon appetito.