Step 1: Preheat the oven

• Preheat your oven to 425°F (220°C). Place a 10-inch oven-safe skillet or cast-iron pan on the stovetop and lightly grease it with butter.

Step 2: Prepare the potatoes

• Use a mandoline or sharp knife to thinly slice the potatoes into even rounds. Pat them dry with a clean kitchen towel to remove excess moisture.

Step 3: Assemble the layers

• Arrange the potato slices in the skillet in an overlapping circular pattern, starting from the center and working outward. Brush the first layer with melted butter, then sprinkle with salt, pepper, and thyme (if using). Repeat the process with the remaining potato slices, layering and seasoning each layer.

Step 4: Cook on the stovetop

• Place the skillet over medium heat and cook for 5–7 minutes to crisp the bottom layer.

Step 5: Bake the potatoes

• Transfer the skillet to the preheated oven and bake for 25–30 minutes, or until the potatoes are tender and golden brown on top.

Step 6: Flip and serve

• Remove the skillet from the oven and let it cool for 5 minutes. Carefully invert the skillet onto a serving platter to reveal the crispy bottom layer. Garnish with Parmesan cheese, if desired, and serve immediately.