Score the lamb in a chessboard-like pattern all over the leg of lamb.
Generously rub the lamb with olive oil, garlic, herbs, white wine, salt, and pepper on all sides.
Place the lamb in a pan and cover with plastic wrap and place in the refrigerator overnight to marinate for at least 12 hours and up to 48 hours.
Preheat the oven to 425°.
Remove the lamb and place it in a pan with a rack and roast at 425° for 25 minutes and then at 350° for 80-90 minutes or until it reaches 135° to 140° internally.
Remove the lamb and let it rest for 15 minutes before slicing and serving.
For the Potatoes: With about 30 minutes left in the cooking process of the lamb, begin to make the potatoes.
Add the oil to a very large frying pan or rondeau pot over high heat until it begins to lightly smoke.
Add the potatoes and onions into the pan and sauté for 10-12 minutes or until they begin to brown.
Place the pan in the oven and cook for 10-15 minutes or until the potatoes are browned and tender.
Serve the sliced lamb along with the potatoes.
