Tip (not mine) for judging how 'done' a steak is: Touch the tip of the first finger of your hand - very gently, don't squeeze AT ALL - to the tip of your thumb. With your other hand, press the flesh at the base of your thumb. That's 'rare'. Touch your thumb to your second finger, and again, press the flesh at the base of your thumb. That's medium rare. You can keep going, but I wouldn't if I were you.
For this you will need:
A metal cooking tray, as one might employ for the cooking of oven chips.
A large bowl, Pyrex or similar, sufficient to cover the steaks (piled up is fine) as they rest.
A heavy-bottomed frying pan, ideally cast iron. I use a Le Creuset that I've had for twenty years that's basically indestructible and I cannot recommend the things highly enough.
A dessert spoon for basting
Almost any cut of beef of any thickness. I have used this technique with 1/3" flank steak, a monster 3" filet (tenderloin), and a full family-sized roast beef joint. I haven't tried it on meat intended for slow cooking (shin, etc).
Remove the steaks from the refrigerator an hour before cooking, season thoroughly with pepper and salt, and then use the back of a teaspoon to coat each side with 1tsp of olive oil. You really can't overdo the seasoning here: go to town. Cover with the bowl until you are ready to start cooking. Then take time out with your family. Enjoy a beer, or a glass of wine. Then, when it is time, return to the kitchen.
Ideally, warm the metal tray. I have a gas hob (grill) so this just takes a few seconds, but it's not mandatory.
Heat the frying pan as hot as you dare. If it's a pan you've used before, it should be smoking.
Seal each steak on each side and edge for a count of 10, then return them to the tray and cover with the bowl. Take the pan off the heat and let the steaks rest for 2-3 minutes.
Take this time to look after the other components of the meal.
Heat the pan again and add a large knob of butter. It should immediately begin to melt and foam. Put one or two steaks (depending on size) at the far end of the pan (you should hear an immediate sizzle) and tilt the pan towards you so that the butter pools at the bottom. Use the spoon to baste the steak in butter for a count of 12. Turn them over, and repeat. If the pan and the butter are hot enough, you should see a fine sheen of bubbles burst on top of the steak as you baste it: this is the oil boiling the juices as they emerge. The liquid butter should also be going a dark, dark brown.
Do this for all the steaks, returning each to the tray as soon as you are done and covering them. Leave for at least two minutes, taking the pan off the heat to avoid smoking out your entire house.
Repeat this process a number of times depending on the thickness of the meat, adding a little butter each time to ensure there's enough to baste with. For reference, tonight I cooked a 1+1/2" sirloin four times in total. Use the touch-test to gauge how cooked the meat is. Each time you return the steaks to the pan you should see them become darker and richer from the dark brown liquified butter you're basting them with, and see the fine sheen of bubbles as the hot oil boils the juices from the surface.
Ideally, save one last cook for just before plating.
Serve, and drizzle a spoonful of juices from the tray over each steak. Squeeze a segment of lemon over them, too.
Note the dark, crisp exterior and uniformly pink interior, with no blood on the plate. This is characteristic: even cuts of meat like ribeye, where there are outlying small pieces prone to overcooking, are served well with this technique.
Now, I'm not a chef. I can feed my family without killing anyone, but I harbour no illusions. This, though - this is genuinely good shit; notably better than good restaurant fare. My wife took me for some Michelin-starred steak for my birthday and we both reckon this is right up there. Nor have I seen this technique described elsewhere - I've used water-baths, I've used pan + oven - this is hands down THE best way to cook beef I've ever tried, and I would love to hear from you if you also enjoy success.