Brush a large sheet of heavy-duty foil with oil. Arrange sweet potato slices, overlapping slighty, over center of foil. Sprinkle sweet potatoes with shallots, rosemary, 1/2 tsp salt and pepper. Fold over foil and seal and place package in or on barbecue. Cook for about 35 minutes, turning package once or twice. (Package can also be baked in a 400F/200C oven for about 35 minutes, or until tender.)

Meanwhile in a saucepan, combine vinegar, maple syrup, mustard, orange peel and remaining 1/2 tsp. salt. Bring to a boil, reduce heat and simmer uncovered, for 10 to 15 minutes, or until mixture is syrupy. You should have about 1 cup glaze. Discard orange peel. Reserve 1/4 cup glaze for garnish.

Pour 1/2 cup glaze over chops and rub in. Grill Lamb for 2 minutes. Brush with 1/4 cup glaze, turn and cook for 2 minutes longer for medium rare.

Drizzle plates with reserved glaze. serve chops on a bed of sweet potatoes.