1.5 pounds Yukon gold potatoes
5-6 tablespoons butter, melted
Fresh ground black or white pepper
1-2 tablespoons minced fresh herbs such as parsley, chives or thyme (optional)
Preheat the oven to 400°F. While the oven is heating, place an 8-inch cast iron skillet or other heavy oven-proof skillet in the oven to heat up.
Peel the potatoes but do not rinse them. Slice them about 1/8-inch thick. (A V-slicer or mandoline makes this much easier.) Discard the end pieces and place the rest in a large bowl. Pour all but about a tablespoon of butter over the potatoes in the bowl. Reserve the rest. Toss the potato slices with the butter until they’re coated evenly.
Remove the skillet from the oven and place it on a trivet or heat-resistant surface. Brush the inside—both bottom and sides—with about half the reserved butter.
Place a potato slice in the middle of the skillet. (Remember, the skillet is hot. Be careful!) Arrange several slices in a circle around the center slice and then continue with another circle, overlapping the slices as necessary to cover the bottom of the skillet evenly. Sprinkle with kosher salt and a few grinds of pepper, and herbs if using. Repeat with the rest of the potatoes; you should have about 5 layers.
Tear or cut a piece of heavy-duty aluminum foil to fit the skillet with at least an inch of overhang. Coat the center of the foil with the remaining melted butter and place it firmly over the potatoes in the skillet, pressing down and sealing the edges of the foil over the sides of the skillet.
Place in the oven and turn the heat down to 350°F. Cook for 40 minutes.
Remove the skillet from the oven. Using a towel or potholder, press down firmly and evenly on the foil to compress the potato layers slightly. Return the skillet to the oven and cook for another 15 minutes. Remove the skillet from the oven and carefully peel off the foil.
Return it to the oven and bake for another 20 minutes. The outside slices should be crisp and deep golden brown and the inside layers soft (test with a skewer or small knife). If necessary, bake for another 5 to 10 minutes.
Remove the skillet from the oven. The slices at the sides of the pan should have pulled away; if not, run a small spatula or knife around the edges. Place a plate over the skillet, and, using a couple of heavy towels or potholders, carefully turn the skillet and plate over so that the potatoes release onto the plate. Serve immediately, or keep warm for up to a half hour in a warming drawer.