How to Make It
Preheat the oven to 450°F. Place either four mini frying pans or one small cast-iron skillet in the oven to preheat.
Shred the potatoes into about 1/16-inch pieces on a mandoline with a julienne attachment. Use your hands to squeeze out as much water as you can from the julienned potatoes. (This will help them brown and crisp when cooking.) Season the potatoes generously with salt and pepper. Let the potatoes sit at room temperature for about 10 minutes, then again squeeze out as much water as you can with your hands.
In a small saucepan, melt the duck fat. Drizzle about ¼ cup of the melted fat over the potatoes. Mix well to incorporate. Place about 1 tablespoon of the remaining duck fat in each mini frying pan, or the full remaining ¼ cup if using a cast-iron skillet. Divide the potatoes evenly among the mini pans, or spread them all evenly in the cast-iron skillet, and place the skillet(s) back in the oven.
Cook for 12 to 15 minutes, or until the röstis are golden and crispy on the bottom. Flip them over and cook for another 6 to 8 minutes, or until golden and crispy on the other side.
Serve the röstis with a generous amount of clabber cream, caviar, and a sprinkling of chives.