Medium-rare sous vide steak – achieving coloring without slicing

The beer cooler hack is not ideal for meat. The issue is the cooking time. I don't find Sous Vide to be particularly good for meats with low fat content that require short cooking time. The meat comes out perfectly cooked, which is nice (i.e. a steak medium rare from edge to edge), but you don't get any real wow factor from the flavor or texture. Where meats start to get really interesting, in my opinion, is long cook times. Tougher cuts of meat that require longer cooking (short ribs, flank steak, ribs, roasts) come out meltingly tender with all the lovely meaty flavor of the cut and you can cook them medium rare. These take 12-24 hours though, and I don't think the beer cooler hack would work for that (at least not without a lot of tending).

However, the beer cooler hack should work very well for seafood, which has much shorter cooking times. Here the temperature control and the vacuum sealing is what really makes a difference. You can get some wonderfully novel textures out of seafood and very subtle complex tastes without anything being "fishy". I'd recommend you try one of the following:

• Salmon Mi-Cuit - cook salmon at 113F / 45C for about 35 minutes. This is delicious. Somewhere between sashimi and cooked, great texture and a fantastic flavor.
• Lobster - cook the tail meat (no shell) at 140F / 60C for 15 - 20 minutes. Do not let this one go long. The lobster will turn to mush and gets disgusting.
• Halibut - cook at 140F / 60C for about 35 minutes. Great texture and flavor. Very moist. Essentially "perfectly cooked" fish.

Note that the first two do not reach pasteurization levels. You should use sushi grade fish and not serve to anyone who is immune compromised.

You could also try chicken breasts. I know a couple of people who rave about chicken because of how moist it comes out, but I've never had much luck with it (the few times I've tried).

Pretty much...yes, but you can fix it!.

When you properly sous vide or very slow cook anything, you'll retain more of the myoglobin color because of the even cooking that often doesn't go above 140 at all. So a properly cooked steak like this will retain much more of its red colored myoglobin. Simply put, the meat will have more red juices to release! (Its a great, great thing about sous vide.)

As @Ronald mentions, the other thing is the resting of the meat. It's an important step as the muscle fibers relax after the heat is off and hold juices better then. An often misstep for the home cook is they allow a hot piece of meat to rest on a flat, solid surface. This causes the bottom of the meat to steam against the board, open the fibers in the meat more, and release the juices on to the board. Rest your meat on a raised baking rack so that it has air circulation all around it.

After a short rest - for most steak 10 minutes is fine, then you can cut into the steak. Use a very sharp knife to slice. The meat here is essentially a sponge and you don't want to compress it and squeeze out the juices. A dull knife will do this and you'll lose more juice on the cutting board again. Use a sharp knife and apply steady, even, but light pressure while slicing - let the edge do the work (if it won't, sharpen the knife more).