1½ pounds (about 4 medium) russet or Idaho potatoes
6 tablespoons butter, melted
⅓ cup olive oil
2 tablespoons chopped fresh thyme
1½ teaspoons kosher salt
½ teaspoon freshly ground black pepper, plus more to taste
¼ cup finely grated Parmigiano Reggiano cheese
Preheat the oven to 400°F.
Lay a potato on a cutting board with a long side facing you. Place a chopstick on either side of the potato. Using a sharp knife, slice the potatoes crosswise into 1/8-inch slices, using the chopsticks as a stopper so you don’t cut all the way through the potato. (Using chopsticks to help out the potatoes is like East and West coming together in peace and harmony.)
Arrange the potatoes on a rimmed baking sheet. In a small bowl, mix together the melted butter, oil, and thyme. Drizzle the potatoes with half of the oil-butter mixture, separating the potato slices slightly so it drips down into the crevices. Season with salt and pepper. Bake until the potatoes start to soften, 35 to 40 minutes.
Remove from the oven, drizzle with the remaining butter-oil mixture, then return to the oven to bake until the potato edges get browned and crisp, 35 to 40 minutes longer. Remove from the oven and dust each potato generously with the Parm. Serve.