Step 1

Preheat the oven to 400 degrees F.

Step 2

Scrub the potatoes, then thinly slice on a Japanese mandoline (about 1/8-inch thick). Place in a bowl of water, then rinse and drain.

Step 3

To a large bowl, add the melted butter, sour cream, half-and-half, pecorino, onion, salt and 2 tablespoons pepper and mix with the potatoes. Butter a 9-by-13-inch baking dish, then place the potato mixture into the dish. Bake until the potatoes are tender and the cream mixture is bubbly, 45 minutes to 1 hour.

Step 4

Meanwhile, in a saute pan over medium-low heat, melt the remaining stick of butter. Let the butter start to foam, then add the potato flakes. Season with salt and lots of black pepper. Gently cook until golden brown.

Step 5

Remove the baked potatoes from the oven and top with the crunchy potato mixture. Finish with more pecorino over the top.