Preheat oven to 450 degrees F.
In a small bowl, whisk together the oil, the butter, and salt and pepper, to taste.
Arrange the potato slices, not touching, in rows on an oiled baking sheet. Brush the potatoes with the oil mixture, and roast them in the upper 1/3 of a preheated 450 degree oven, turning them once with a spatula, for 18 to 22 minutes, or until they are golden and crisp.
Transfer the potatoes to paper towels to drain, sprinkle them with the coarse salt and pepper to taste, and serve them warm.
Recipe courtesy of Gourmet Magazine