Place the potatoes in a large saucepan of salted
water, cover, bring to the boil and simmer for 5
minutes. Drain and leave to cool.
Grate the potatoes coarsely into a mixing bowl and
add the grated onion. Stir in the beaten egg and
season to taste with salt and pepper.
Heat the
butter in a frying pan and add the potato mixture,
spreading it over the pan. Cook over a moderate heat
for about 15 minutes until lightly browned on both
sides.
There is no need to turn all the potato at
once just lift one section on to the spatula at a
time and turn it over carefully.
Use the spatula to
press the potato together to form a large pancake,
then cook for 2-3 minutes until the underside is
browned and crisp.
Invert the pancake on to a plate, slide it back into
the pan and cook the other side. Cut into wedges and
serve immediately.