Preheat a grill to medium-high and lightly oil the grates. Preheat the oven to 400 degrees F. In a small pot, melt the butter with the garlic and Sichuan peppercorns over low heat. Stir and cook for 2 minutes. Sprinkle over the brown sugar, and cook for an additional 1 to 2 minutes, stir and remove from the heat. Toss the sweet potatoes in 1 tablespoon vegetable oil, and season with salt, to taste. Grill the sweet potato slices on both sides, achieving grill marks. Transfer the grilled rounds to a baking dish and spoon the garlic butter mixture over the sweet potatoes. Roast the potatoes for 20 to 25 minutes, or until they are tender and cooked through.
Recipe courtesy of Roger Mooking