1. Cut edges off potato kugel and mash.
2. Add egg and oil.
3. Add to pan. Fry until golden and either flip or roast in 475-degree-Fahrenheit oven as per above.
4. While it fries, mix sour cream, grated horseradish, and white pepper together.
5. Top finished rosti with Old Williamsburg smoked salmon, the horseradish sour cream, pickled onions, and fresh herbs of your choice (dill, oregano, parsley, and chives all work).