Peel and grate 565g of russet potatoes and ½ small yellow onion. Squeeze them as dry as possible in a clean kitchen towel, then toss with ¾ teaspoon of salt and ¼ teaspoon of black pepper.
Heat half of 2 tablespoons of vegetable oil and half of 2 tablespoons of unsalted butter in a large skillet over medium-high heat. Press the potatoes into the pan in an even layer.
Cook, undisturbed, for 6-8 minutes, until golden brown and crisp underneath. Flip, add the remaining oil and butter to the pan, and cook for 4-5 minutes more, until golden brown.
