Preparation

• Position a rack in the center of the oven, and heat the oven to 400°F.
• In a 10-inch nonstick ovenproof skillet, melt the butter over medium-low heat. Add the sage and cook, stirring, until the butter is just beginning to brown and the sage is crisp, about 1 minute. Add the garlic, and cook for another 15 seconds. Remove the skillet from the heat, and transfer about three-fourths of the butter mixture to a small bowl, leaving the rest in the skillet. Starting in the center and working in concentric circles, layer the potatoes in the skillet. Evenly brush with the reserved butter, making sure each layer gets some of the sage and garlic. Season generously with salt and pepper as you go.
• Transfer the skillet to the oven, and bake, rotating the skillet occasionally, until the potatoes are tender and deep golden, 40 to 50 minutes. Remove the skillet from the oven, and allow to cool for 10 to 15 minutes. Run a thin spatula or knife between the edge of the potatoes and the pan, then invert onto a serving platter. Finish with flaky sea salt, if using, and serve.