I'm going to provide some important insight into this step. But first, I want to explain why it is necessary.
Alton Brown is one of my favorite cooking educators. He does a show where he cooks the exterior of a steak, first on high heat in a cast-iron pan on the stove, then transferring it to the oven to cook the internals to the proper desired finishing temperature. He then transfers it to an inverted plate for the juices to run away from the steak in order not to dilute the browned-surface of the steak while it rests....so far, so good.
Alton has two things going on here while he lets the meat rest. The first is a method to prevent the juices that are still seeping from the meet to form a pool that the steak is sitting in. This pool of fluids will dilute the browned crust that he worked so hard to put on while browning it in the cast-iron pan.
But why does he want it to rest in the first place?
Meat contains a lot of liquid. I know this first hand from cooking BBQ using big pieces of pork. Slow roasting cooked BBQ will reduce the weight of the meat by around 30%! This is lost moisture, not lost meat.
When I was just starting the process of automating my cooking of BBQ (after the novelty wore off, I got tired of staying up all night tending a smoking fire), I inserted multiple channels of thermocouples into the cooking environment. Some were in the combustion chamber (where the wood was burning), some were in the smoking chamber (where the meat was cooking), some were in the exhaust stack (where the smoke exited the cooker), and some were outside in the ambient air. Some were also inside the meat. I placed some on the surface of the meat, and buried several more, each going about 1 inch deeper than the previous thermocouple, until I had reached the middle of the meat.
I then proceeded to cook the meat using a controller that I built that would precisely control the temperature of the smoke chamber to within 2 degrees by opening and closing the inlet air damper.
From this series of tests, I was able to note an interesting thing. The internal temperature of the meat would gradually increase, in a logarithmic manner manner (temperature increasing faster at first, but gradually the increase grew slower and slower until it more-or-less flat-lined). This internal meat temperature would hold steady for hours....and then the temperature would start taking off higher again!
What the heck was going on? The combustion chamber, smoke chamber, and exhaust stack were not changing temperature, yet the internal temperature of the meat was suddenly climbing after hours of not moving. So what was going on?
Well, I'll tell you. The meat had been seeping moisture from the internals to the surface of the meat, where it would evaporate in the hot smoking chamber. You could not actually see this moisture moving away from the meat. But it was moving off of the surface of the meat, leaving behind brown-goodness, AKA Maillard Browning. This fluid, moving off of the surface of the meat into the air of the smoke chamber works the same way your skin works in perspiring - the fluids you perspire evaporate away from your skin, taking heat with it, and keeping your body cool.
The meat, in having fluids move to the surface, where it evaporated into the smoke chamber's air, was removing heat from the meat. So, as soon as the meat ran out of fluids that could remove the heat through evaporation, the internal temperature of the meat started to rise. So when this occurs, you have direct evidence that the meat has given up it's moisture and now is a heavy slab of dried out meat.
So what makes the moisture move to the surface of the meat anyway? Obviously heat is involved. And when you heat something with water in it that is enclosed, then the internal pressure of the meat is raised. So by heating the meat, the fluids inside the meat are heated, and this heat raises the pressure of the fluids trapped within the cell walls. Rising the temperature high enough and long enough will cause the fluids to push their way out of the cells, and eventually cell wall to rupture and release all of the remaining fluids.
So pressure, due to increased temperatures, pushes the fluids out of the meat. And fluids leaving the meat take heat from them. And if the temperature of the oven is low enough, then there will be a balance struct between the internal temperature of the meat and the temperature of the smoke chamber - the internal temperature of the meat will stay constant, as long as moisture remains in the meat. As soon as the meat runs out of moisture, the internal temperature of the meat will start to climb. Now, this can be overcome if the oven temperature is significantly higher than the temperatures used in cooking BBQ, just like your body can be overheated while perspiring if the outside air temperature is high enough.
So I can observe this when I make BBQ, because I cook mine at 185 - 190 typically, for a period of 24 hours. And it's an interesting thing to see.
So all of this to get back to the one thing - how to properly rest the meat.
We now know why we want to do this - by removing the meat from the heat source, we are allowing the internal temperature of the meat to lower, and we now know that this lowering of internal temperature will result in lower pressure, so the fluids will no longer be squeezed out of the meat. And assuming you don't want dry meat, this is a good thing!
But the last piece of this puzzle is how to allow the meat to cool (or rest) so that the outside Maillard Browning crust isn't diluted by the pooled fluids?
Alton Brown using an inverted dish to place his meat on while enclosing the whole thing inside aluminum foil. But this is sort of awkward.
Instead, I put my steak to rest on a pie-cooling wrack (it stands just 1/4 inch above the surface it rests on). I put down a piece of aluminum foil, set the pie-cooling wrack on it, then the steak, then tent the whole thing and let it rest this way for 10 minutes, and bingo! I've got my perfect cooked steak.
My whole method for cooking steak indoors:
- Heat a cast-iron pan on the stove on high heat with just a little bit of oil in it, preferable canola oil as it can take higher heat best. The oil is really there to help transfer the heat to the steak from the pan.
- When the oil just starts to smoke, reduce the heat a little and immediately add the steak to it.
- Brown on one side until it reaches a deep dark color before flipping to the other side. Watch for smoke - if it's producing a lot of smoke than it's too hot and cut it back a little. You'll just have to experiment with this.
- Cook this second side until it's done like the first side.
- While this is being performed, place a pie-cooling rack onto a plate large enough to let the rack stand on.
- Cut the heat off.
- Transfer the steak to the pie-cooling rack so steak fluids don't dilute the surface browning.
- Now transfer the pie-cooling rack, which has the steak on it, to the top of the pan. My pie-cooling rack overlaps the top edge of my pan so that the steak is sitting on top of the pan on the rack.
- Transfer the whole pan-and-steak to the oven, placing it into the top 1/3 of the oven preheated to 325 and cook it for about 10 minutes without turning.
- Put a piece of aluminum foil onto a plate. This should be large enough for the pie-cooling rack and steak to sit in and be wrapped up on all sides, forming a tent.
- Remove the pie-cooling rack with steak and place onto the aluminum foil, then bring together and crimp all sides without letting it touch the steak on the sides or on the top.
- Leave it to sit for 10 minutes - resting.