It's already a bit passe, but sous-vide ("under vacuum") is a method of cooking which involves sealing food in air-tight plastic and cooking it in a tightly temperature-regulated water bath, usually at a low temperature for a long time. The main advantage is that this method is basically the only way to cook something while keeping the integrety of the food completely intact. You essentially (in theory) end up with every molecule you started with in the final result.
Here is an experiment I did with sous-vide duck breast:
1. Start with a nice duck breast, with some garlic, orange peel, thyme, salt and pepper.
2. Seal it all together in an air-tight plastic bag that can withstand near boiling (I used a cheap Seal-a-Meal...but these machines can be ridiculously expensive).
3. Immerse in a water bath that is maintained at around 130F (a laboratory thermoimmersion water bath would be best, but I just balance a thermometer on the edge of the pot and adjust the heat). The larger the volume of water you can use, the more constant the temperature will be. Let this sit in the water for 2 hours..up to 12 hours (at maybe a slightly lower temperature).
4. Remove the breast and open the bag carefully.
5. Essentially, it's done.
The next steps are optional:
6. Fire it in a pan to crisp up the skin.
7. Remove it to a plate.
8. Deglaze the pan with a little Gran Marnier. Set it afire.
9. Serve it with some watercress. Yumm-o!