Pity you don't have an onion or any herbs but you have the basics of a spanish omlette
Edit: Great, here we go.
Slice your potatoes into thin slices and boil for about 20 minutes till they are just cooked.
Put them in a frying pan, laying them out in a couple of layers. Mix in slices of your spring onion so they are pretty spread out. Beat some eggs together and add your oregano. Pour over your potatoes and fry on a lowish heat till just about cooked.
Grate your cheese and add to the omlette. Then take the pan and put under the grill till the cheese is all melted and yummy.