This has made me sooo hungry. I'll have to make some - but which version? I usually use cheddar but vary condiments - grated and mixed with thinly sliced spring onion (ordinary, if no spring onion) with a dash of Tabasco, or plain with grated black pepper added after cooking, or as before but served with a side of ice cold firm tomato, or toast smeared with tomato pesto and then topped with a mix of grated cheddar and parmesan.
I even used to do a version that my son loved which was tuna mixed with a little mayo, chopped sundried tomatoes and sweetcorn covered with cheddar. When I was a child my mother, obviously ahead of her time, used to make a "deconstructed" cheese on toast - she would layer cheese and onion in a saucer, grill and serve with toast so you could spread the cheese on the toast as you ate it. She would also crack an egg in a saucer, top it with slices of cheese and grill, being in a shallow saucer the egg would spread out and cook quite quickly. Who thought this thread would lead me on such a trip down memory lane!