I want to cook an entrecote using my sous vide waterbath. The piece is approx. 5cm thick and currently frozen. I would like it to come out as medium-rare. It has a quite a bit of fat on it. At what temperature and for how long should this piece be cooked?
My own guess would be 3 hours at 57, but I after googling my eyes out, I see several different numbers that diverge to a confusing extent.
I confess I'm not familiar with the term entrecôte, but looking it up, its pretty clear this is a already-tender cut. So you don't need to tenderize it.
In fact, you probably don't want to tenderize it—at some point, it'll go from tender to mushy. Unfortunately, from frozen, at least according to the Baldwin tables, you'd need over five hours. If you additionally want it pasteurized, that'd probably be over six hours, but he doesn't have a table for that. Either of those times is risking mushy, at least on the outside.
You can reduce the heating time substantially by thawing it in the fridge. This also gives you the opportunity to sear before bagging (killing any surface bacteria, and also improving flavor). You're probably looking at around 3–3½ hours this way (maybe up to 4 for pasteurization, depending on exact thickness).
Finally, once its thawed, you could split it in half, giving you two, 25mm steaks (split before searing, of course). Then you're looking at around an hour in the water bath, or two for pasteurization.
Even with a pre-sear, you'll want to sear after cooking as normal, too.
Your final option is to up the water-bath temperature a bit, and pull before the steak reaches thermal equilibrium. Basically, the last few degrees take forever—heat transfer is proportional to the difference in temperatures—so if you're OK with a doneness-gradient, as you'd find in traditionally-cooked steaks though not as extreme, you can do this. Problem is, I don't have a table for this, so I'm not sure what the time would be at, say, 59°C. You could attempt to rig it with a probe thermometer to find out, but beware cheap probes are not waterproofed where the wire enters, and will be break if water gets there. There are i-Device apps that will calculate these times for you (PolySci Sous Vide Toolbox, Sous Vide Dash) but I haven't used either (no Android versions...) [This is called the deltaT method]
There are clearly many ways to approach this. This is a fairly thick, probably rib-eye steak. I would pre-sear while frozen, bag with a small amount of oil or butter, and cook at 55 or 56 for 3 hours, then season (do not season before the initial cook) and sear again before serving to develop a flavorful crust.
