Method

Peel and coarsely grate the parsnips and put into a large bowl. Add the egg, cornflour or arrowroot and a couple of good pinches of salt. Mix well to combine.
Heat a heavy-based frying pan over a medium heat and grease the four crumpet rings, or other metal rings. Add 2 tsp fat to the pan and let it melt.
Pop the metal rings into the pan and fill with the parsnip mixture, packing it down a little: it should be no more than 2cm thick, or they won’t cook through. If you don’t have any rings, simply make little piles of the mixture in the pan and squash them down a bit.
Allow the rösti to cook for a few minutes and then check the underside by lifting it up with a palette knife. If the underneath is deep golden brown, lift off the rings using tongs or a tea towel and turn the rösti over to cook the other side. If you struggle to get the rings off, just run a butter knife around the inside of each one.
Serve the rösti straight away, topped with a knob of butter or a dollop of crème fraîche, or just as they are as a side dish.