For Christmas, Santa brought me a copy of Thomas Kelleher's Under Pressure: Cooking Sous Vide - a cookbook largely devoted to the sous vide technique of cooking. Sous Vide, or under vacuum, is a bit of a misnomer but refers to cooking things sealed in vacuum bags in a water bath.
There are three reasons people use sous vide. First is that you can intensely flavor whatever you are cooking. Since the bag is sealed there is no chance for flavors to evaporate; instead they go into the food. Secondly is for precise temperature control - this is what makes sous vide at home such a challenge. Finally can get a sort of compression. Mellon has been the popular example. You can take a 5" cube of watermelon and compress it into something about 1/2" that has a much different texture.
Sous Vide requires two pieces of equipment. First, you have to have a way to vacuum seal the food. The $100 FoodSaver from Tilia does a fine job (although it will not provide much compression). The challenge comes with the temperature control part. Professionals are using laboratory-grade 'immersion circulators' which can keep a container of water at a perfectly controlled temperature. The only problem - they cost $1,000.00. That makes impressive tricks like preparing salmon that looks raw but is actually cooked a challenge. You need water that is exactly 104 degrees F. 103 and 105 simply do not work, its a protein coagulation thing.
(Worth noting, Grant Achatz has demonstrated sous vide in zip top bags - you can find the video here)
The good news is that the technique still has a place in the home kitchen. Some foods, like vegetables, are very forgiving and can withstand the fluctuation that you get using a pot of water and thermometer on the stove. We tried some green olive and grapefruit poached fennel that was outstanding. The olive and citrus flavor was pronounced throughout the fennel and it could not have been easier. We prepped a bag with sliced fennel, some crushed green Spanish olives, grapefruit slices and great olive oil and set it into a pot of water that we tried to keep around 160 degrees F. It took about two hours for the fennel to soften up, but the remarkable thing was how green and crisp they stayed. Another forgiving food are scallops. Scallops are almost all protein and work very well in sous vide. We did ours with bacon fat and bay leaves. After rendering the bacon, I let the fat cool and poured enough in to cover the scallops which had been seasoned with a little gray salt. After that I tossed in a few fresh bay leaves and sealed the bag. 1 hour in a 120 degree F bath and they were cooked perfectly through and had a wonderful texture. The bacon flavor was intense but not over powering.
I am looking forward to working through Under Pressure and learning more about the technique, but I am excited to know that at least some part of sous vide is in reach for the home cook.