Using a box grater, grate your half-baked potatoes.
Season with 2 tsp. Kosher salt, 1 tsp. ground pepper, and a pinch of nutmeg.
Heat a 10-inch cast iron or non-stick skillet over medium-high heat.
Add 2 tbsp. clarified butter in the pan.
Add potatoes, and using a flexible spatula, form them into an even disc, about 1 inch thick. Cook until deep golden brown and crisp on the bottom, about 10 minutes; lower heat to medium.
If I feel it is getting dry, I will add a little clarified butter around the edges at about the 5-minute mark.
After 10 minutes, Set a plate on top and flip to invert rösti.
To the pan, add 2 tbsp clarified butter and slide the rosti back into the pan.
Cook for 10 more minutes.
Slide the rosti out of the pan onto a cutting board and cut into quarters to serve.