Preheat the oven to 200°C. Combine the rosemary, garlic and olive oil and rub the mixture all over the pork loin. Season with salt and freshly ground black pepper. Place in a roasting pan and roast in the oven for 40 minutes or until an internal temperature of 63°C is reached. Remove the roast from the oven, take the pork from the pan and set aside to rest so the juices redistribute through the meat. Meanwhile, place the roasting pan on the stovetop and bring the pan juices to a simmer. Add the wine, Simon Gault Home Cuisine chicken or vegetable stock and 2 sprigs of rosemary, then simmer until reduced by half. Add the hazelnuts and bring to the boil. Remove the rosemary and add the butter. When it is almost melted, turn off the heat and give the pan a quick shake to emulsify the sauce. Slice the pork, place on a large platter and spoon the hazelnut sauce over and around the pork. Garnish with a sprig of rosemary.