Place the frying pan over a medium heat, with ½ tablespoon of fat left from frying bacon (or groundnut, grapeseed or olive oil) in it.
As soon as it is hot (with a very faint shimmer on the surface), carefully break in the egg. Then turn the heat down to low and carry on cooking, tilting the pan and basting the eggs with the hot fat so that the tops of the eggs can be lightly cooked, too.
After about 1 minute, the egg will be ready, so remove the pan from the heat and then lift it out with a slotted kitchen slice.
Let it rest on some kitchen paper for a couple of seconds before putting it on a warmed plate and eat as soon as possible.
If you would like to fry your eggs in butter, then you need to use a gentler heat and give them a bit longer, so the butter doesn't brown too much.