1: Wrap the potatoes and 3 tablespoons butter in heavy duty foil. The potatoes should be in a single layer. Arrange the resulting packet directly on the coals. Cook the potatoes until soft (they’ll crush when pressed through the foil), turning every 5 minutes with tongs. The total roasting time will be 20 to 30 minutes. Transfer the potatoes to a sheet pan and keep warm until serving.

2: Just before serving, melt the remaining butter in a large cast iron skillet or on a plancha and heat until sizzling. Unwrap the potatoes and place in the skillet. Flatten with a grill press, the back of a small skillet, or a potato masher. Sizzle the potatoes in the hot butter until crisp and browned, 3 to 5 minutes per side, turning with tongs. Season the potatoes on both sides with salt and pepper.