Heat oven to 425°F. In 10-inch ovenproof skillet, drizzle 1 teaspoon of the melted butter. Layer with half of the potato slices, thinly overlapping. Brush with 1 teaspoon butter. Layer with all of the apple slices. Sprinkle with salt, pepper and 1 1/2 teaspoons of the sage. Layer with remaining potato slices. Drizzle remaining 3 teaspoons butter over top. Sprinkle with salt, pepper and remaining 1 1/2 teaspoons sage.