Put the spring onions and potatoes through the food processor grater, or grate them by hand.
Putting a handful in your palm, squeeze any liquid out of it and put into a bowl. Continue until you have squeezed dry all the mixture.
Then mix in three eggs and the parmesan. Season to taste.
Squeezing a small handful of mixture, place it in a frying pan of hot olive oil. Press it down with a fish slice. Continue to add small mounds of mixture to the pan, leaving space for pressing down between potato patties.
Allow the bottom to go golden then carefully flip over the rosti.