Grate potatoes and onions.
Place in a cheese cloth over a sieve and squeeze ALL the liquid out into a bowl.
Let the liquid sit, the potato starch will fall to the bottom of the bowl.
Pour off the liquid and mix the grated potatoes and onions with the potato starch.
Add the egg and mix in well.
Season with salt and freshly ground black pepper.
Heat oil in a frying pan and let it get really hot.
Take a spoonful of the mixture, place on the pan and flatten lightly with a spatula.
Once crispy on the bottom, flip the latke and crisp the other side.
When cooked, place latkes on a plate with kitchen roll and sprinkle with flaky sea salt.