1. Line a 9x5-inch loaf pan with parchment paper, allowing edges to extend beyond the sides of the pan.

2. Peel and slice the potatoes lengthwise using a mandoline, to 1/16-inch. Place in a extra-large bowl; cover potatoes with water. Add the cider vinegar. Gently stir and let stand for 30 minutes. Drain well and pat very dry. Preheat oven to 250°F.

3. Return potato to the same bowl. Add beef tallow, and salt. Gently toss to coat.

4. Arrange slices layer by layer, filling gaps in the previous layers as you go. Cut a piece of parchment to fit over the top of the potato layers.

5. Bake 3 hours or until fork tender.

6. Remove top parchment paper, cover potatoes with plastic wrap. Place a second loaf pan of the same size on top of the potatoes. Weight with several cans of food. Chill in the refrigerator 12 hours.

7. Remove weights. Lift potatoes form pan using the edges of the parchment. Cut the stack of potatoes into 32, 1-inch pieces.

8. In a deep, heavy saucepan, heat 1 1/2-inch of oil to 375°F. Fry 6 to 8 potato pieces at a time until golden brown and crisp, 3 to 4 minutes. Sprinkle with additional salt. Serve with Horseradish Sour Cream.

Horseradish Sour Cream

1. In a small bowl, whisk together sour cream, horseradish, and chives.