In a small bowl combine the garlic, rosemary, 1 tablespoon of the salt, anchovies, 4 tablespoons of the olive oil and the white wine vinegar and stir to form a paste. Using a sharp paring knife, make evenly spaced deep slits all over the roast and stuff the slits with as much of the paste mixture as you can. Using your hands, rub any remaining paste all over the sides of the lamb and place the lamb in a baking dish. Cover with plastic wrap and refrigerate overnight.
Remove the lamb from the refrigerator and allow to come to room temperature. Preheat the oven to 375 degrees F.
Remove the plastic wrap from the lamb and add the white wine and chicken stock to the bottom of the baking dish. Rub the lamb all over with the remaining tablespoon of olive oil and sprinkle with the remaining teaspoon of kosher salt and the black pepper. Transfer the lamb to the preheated oven and bake, uncovered, basting occasionally with the pan juices, until an instant-read thermometer inserted into the thickest part registers 130 to 140 degrees F. for medium rare, about 1 hour and 15 minutes. Remove the lamb from the oven and let rest for 10 to 15 minutes before carving. Serve slices of lamb with some of the pan juices ladled over the top. Garnish with the chopped parsley and mint before serving.