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.