"Sous vide" is French for "under vacuum" and cooking en sous vide typically refers to vacuum packing ingredients, then cooking them under very strict temperature control. "Precision cooking" might be a more accurate term, but all gastronomical things tend to gravitate toward the French descriptions. When sealed in plastic, the aromatics cannot vaporize so flavors are more intense, and food can be cooked in water baths held at specific temperatures for long periods of time without the water soaking or otherwise changing the texture of the food. Sous vide is a food service technique that has been embraced by the world's best chefs, and with some equipment that is not outrageously expensive, you can duplicate some of their dishes.
My two favorite references for sous vide are Thomas Keller's Under Pressure and A Practical Guide to Sous Vide Cooking by Douglas Baldwin.
Here's the short form of the recipe:
Salt and vacuum pack as many beef ribs as will fit in your water bath (I prefer grass-fed beef).
Cook at 135 F for 48 hours.
Sear with propane torch.
Eat immediately - sharing is optional.
Step 1: Sous Vide Equipment
Sous Vide Magic PID temperature controller purchased from Auber Instruments on Ebay
cheap crock pot1 without electronics (just an on/off switch)
FoodSaver Vac 200 (the link goes to a model that's close enough) Vacuum Sealing Kit (borrowed from helava)
Update: since I purchased my equipment, Sous Vide Supreme has started making an all-in-one unit designed for home use. The regular 10L unit is $400, and the still-quite-roomy 8.7L Demi is $300 - comparison here.
1 A rice cooker or electric kettle can also work; the variables are size of container, and speed of heating. I usually pre-heat the water, as crock pots heat up VERY slowly. We've got an industrial-sized rice cooker on order. The key is to make sure your heating device doesn't have a brain, as the PID controller works by cycling the power on and off and you can't be resetting your crock pot each time.
Step 2: Salt the Meat
Step 3: Vacuum Pack the Meat
I'm using a "channel-type" vacuum sealer; professional chefs will use a chamber sealer. The primary difference is that a channel sealer has difficulty sealing liquid into the bags (because it tries to suck the liquid out). That doesn't matter for this recipe, but for other sous vide recipes I get around this by freezing the liquid ingredients, then vacuum-packing them as solids.
Step 4: Precision Cook the Meat
I found my crock pot to work fine for this recipe, and to have good temperature stability and homogeneity. It is, however, a poor choice for short sous vide cooking because of its relatively low power. It cannot respond quickly to fluctuations (say throwing in a pound or two of 40 F meat). If you want to cook a piece of sirloin for 30 minutes at 125 F, the crock pot can be frustrating to use. I've got my eyes peeled for a used large commercial rice cooker...
After two days, take the meat out of the vacuum bag. The small amount liquid is tasty, and due to the melted collagen and gelatin will solidify when it cools. Be sure to reserve it for use in stock or gastrique.
Step 5: Sear the Outside of the Meat
Searing temperatures are much higher than cooking temperatures, especially sous vide cooking temperatures. If you bring an entire piece of meat to searing temperatures, it will be overcooked and dry, so you only want to sear the outside. This way you get all those nice Maillard reaction products and seared-meat smells on the surface, and perfectly-cooked meat on the inside.
Here, I'm using a propane torch to sear the outside of the beef ribs. Briefly pan frying them in hot oil, or putting them on a hot grill also works. Note that we're only talking a minute or so - this really is just for surface effects.
Step 6: Immediately Eat
Alternatively, serve them as the main dish at a super-fancy dinner party. Either way, they'll probably be the best ribs you've ever tasted. While you can add the sauce of your choice, it really is gilding the lily.
Strip every bit of meat off the bones, and lick your fingers. Save the bones for making stock - I just bag them and toss them in the freezer for later.