This colourful and impressive side dish can be prepared on the hotter side of the grill while steaks cook on the cooler half.
1 lb sweet potatoes
1 lb purple potatoes
1/4 to 1/3 cup butter, melted
1/2 tsp salt and freshly ground black pepper
Peel the purple and sweet potatoes, then slice them thinly using a mandoline or food processor.
Generously coat the bottom of the pan with 1 tbsp butter. Arrange purple-potato slices in a thin layer on the bottom of a 9-inch round foil pan, overlapping their edges slightly. Lightly brush them with butter and sprinkle with salt and pepper. Repeat with remaining potatoes, layering the sweet potatoes and then the purple ones until all of the ingredients have been used. Press firmly into the potatoes to pack them down and seal the pan with foil.
Preheat barbecue to medium-high heat. Reduce heat on one side of the grill until the barbecue reads 300 to 350 F. Place the pan on the hot side of the grill. Grill until almost tender (about 20 to 30 minutes). Carefully remove the foil that is covering the pan and set the foil aside. Continue barbecuing the potatoes until they are tender (about 10 minutes more). Remove from the barbecue and loosely cover with the foil. Let stand until ready to serve, then, just before serving, cut the potatoes into wedges.