Directions

• Scrub potatoes with vegetable brush under cold running water; peel potatoes. Shred on a box grater or with the shredding blade of a food processor.
• Take a handful of the shredded potatoes and squeeze to remove excess liquid. Place in large bowl and repeat with remaining potatoes. Stir in onion, flour, thyme, salt, and pepper.
• Over medium heat, heat a 10-inch skillet. Add 2 teaspoons of the oil and 1 ½ teaspoons of the butter and heat until butter melts and foams.
• Add potato mixture, spreading evenly in the pan, pressing down with a spatula to form a disk. Cook until the bottom is golden brown, about 11 to 12 minutes.
• Carefully slide the rosti onto a plate, Invert a second plate over the rosti and flip over so that the browned side is now on top.
• Return skillet to the heat. Add remaining 2 teaspoons oil and 1 1/2 teaspoon butter and heat until melted.
• Slide the rosti back into the skillet and cook until the second side is golden brown and crisp, about 6 to 7 minutes longer.
• Slide rosti out of pan onto serving plate or cutting board. Cut into four wedges and top with sour cream to serve.