How to make pan haggerty

One of my favourite meals is pan haggerty and it is very simple to make. Potatoes, onions and cheese are the ingredients. Slice the potatoes and boil them for about 10 minutes. Then drain them (keep the water to make into a soup) and in a deep pan put in a layer of potatoes, then of onions and then a handful of grated cheese. If there are ingredients still left, do another set of layers. Then cook on a lowish heat for about 20 minutes.