Here is some info from ColinMcNulty.com:
What is a Blue Steak?
If you think about the difference between well done and rare, well there is just as much difference between rare and blue. It’s way beyond Very Rare. I’ve seen “blue steak” variously described as: take a cow, rip off any horns, wipe it’s arse, and throw a match on it; or my personal favourite: steak so rare, a good vet could bring it back to life!
Don’t get me wrong, a blue steak is not Steak Tartare (which is completely raw), it is cooked though of course definitions vary as to what “cooked” means when it comes to a blue steak.
Here is a chart that may explain things, or at least make this article seem longer:
Here, also from from ColinMcNulty.com, is advice on how to cook a blue steak:
Get the best bit of steak you can: go for fillet steak if you can get it, or sirloin steak, or if you must rump steak.
However, also try to get the thickest cut possible.
If you can, leave it out of the fridge for a few hours before cooking. This is to bring the steak up to room temperature, which will help the middle become warm, considering the quick cooking time (2-3 minutes).
Salt and Pepper the steak to taste, I like a bit of sea salt and a lot of cracked black pepper corns. You can also add some herbs if you like, a sprinkling of rosemary is my favourite.
Heat some (extra virgin) olive oil in a large frying pan. Set the heat to HIGH, you want it HOT.
Pop in a small nob of butter, which should bubble immediately.
Now carefully place your soon to be blue steak in the frying pan. Try to leave it alone, don’t fuss over it. No stirring or prodding, no weighing it down or pressing, the occassional shake of the pan should be all that’s required to alleviate your worries that it might be sticking.
Make sure the heat is still on high.
If your steak is thin, after 1 minute, that side will be done so turn it over.
If your steak is thick, you might be inclined to stretch to 1.5 mins per side.
After the 2nd side is done, you should ensure that no part of the surface of the steak is still uncooked. If you have a particularly thick steak, it’s possible the sides aren’t cooked, so manipulate the steak to slowly roll it round on its side.
Posted by Guy Hutchinson