- 3 large russet potatoes (about 1 1/2 pounds), peeled
- sea salt and freshly ground black pepper, to taste
- 4 tablespoon unsalted butter, melted
- 2 tablespoon extra-virgin olive oil
- Cut the potatoes into a fine julienne with a mandoline or with the coarse shredding blade of a food processor. (Once they are grated, do not rinse the potatoes; you need their starch to hold the potatoes together.)
- Transfer them to a baking sheet, season well with salt and pepper, and let sit for a few minutes. Place the sheet on a tilt; the salt will begin to wilt the potatoes and they will begin releasing water.
- Heat 1 tablespoon of the butter and 1 tablespoon of the oil in a 9- or 10-inch nonstick skillet over medium heat. Squeeze the potatoes very hard between your hands to remove as much water as possible and then add them to the pan. With the back of a large spoon, neaten the edges and lightly press the potatoes to make a flat cake.
- Cook for a few minutes and then rub all around the edge of the pan with a tablespoon-sized nut of butter so that it melts and runs under the potatoes.
- Cook over medium heat until crispy and brown, about 10 minutes. Slide the cake carefully out onto a plate, cover it with a second plate, add another piece of butter to the pan, and then invert the plates and slide the cake back into the pan to cook the second side.
- Cook, adding butter or oil as needed around the edges and tilting the pan, until the cake is crispy underneath and the potatoes have cooked through, 7-10 more minutes. Regulate the heat so the cake browns and caramelizes but does not burn.
- Slide it onto a cutting board, blot any excess oil with paper towels, cut into 8 wedges with a sharp knife, and transfer to a large round serving platter. Season with salt, to taste, and serve immediately.