Boil potatoes in their jackets until tender.
When they have cooled, peel and thinly slice.
Heat butter in a large frying pan, and add potatoes, seasoning well.
Turn frequently until golden brown.
Mix in 75 g / 3 oz / 1 cup of cheese with the potatoes, and form into a flat cake.
Top with remaining cheese, cover, and fry until cheese melts.
Turn out on to a warm plate, with crusty side uppermost.