Heat the oven to 375°F and place a rack in the middle position.

Generously grease a 10- to 12-cup ring mold or Bundt pan with butter or neutral oil, getting into every crease if using a decorative Bundt pan.

Peel the potatoes and keep them in a bowl of cold water while you work so they do not brown, then slice them into thin rounds about 1/8 inch thick.

In a large bowl, whisk together the melted butter, heavy cream, kosher salt, and black pepper if using.

Pat the potato slices dry with a clean kitchen towel, add them to the bowl, and gently toss until every slice is coated in the buttery cream mixture.

Arrange the first layer of potato slices in the bottom of the prepared mold, overlapping them in a neat circular fan because this layer will show when the ring is unmolded.

Continue layering the potato slices, overlapping and pressing them down lightly as you go, spooning some of the remaining cream mixture over every couple of layers until all the potatoes and liquid are used.

Cover the mold tightly with foil, set it on a rimmed baking sheet, and bake for 45 minutes.

Carefully remove the foil and bake uncovered for another 30 to 40 minutes, until the potatoes are very tender when pierced with a knife and the top edges are deep golden and crisp.

Remove the mold from the oven and let it rest on a cooling rack for 10 to 15 minutes so the ring can set and hold its shape.

Run a thin knife or flexible spatula around the inner and outer edges, place a warm serving plate upside down over the mold, flip confidently with oven mitts, lift the mold straight up, dab away any pooled butter or cream if desired, and slice into wedges to serve hot.