Pre-heat oven to 425 F degrees.
Shred potatoes and onions with the grating disk of a food processor.
Place potato and onions shreds in a salad spinner and spin the excess water out. Keep spinning away to dry out as much as possible.
In a large bowl, whisk together the eggs, parmesan cheese, green onions, salt and pepper. Add potatoes and onion and stir to incorporate.
Place a well-seasoned, 12-inch cast iron skillet over high heat and add olive oil.
When the oil is shimmering, add the potato pancake batter and pat ir firmly into a single, even layer.
Cook on the stovetop for 5-6 minutes, until the bottom is starting to brown and set.
Transfer skillet to preheated oven and bake for 8-10 minutes.
When the pancake seems cooked through, switch to the broiler and cook until the top is quite brown and crunchy. Keep a close eye on it!
Remove the pancake from the oven and let cool slightly. Top with sour cream, applesauce and/or chives. Can’t cut into wedges straight from skillet or by sliding pancake onto a cutting board. Serve and enjoy.